First draft of an European Project

ALFA PROGRAMM
Contract No.: AML/B7-311/97/0666/II-0147-FI
Title
“Measurement methods involving high magnetic fields for advanced and novel materials”
HIFIELD

1. Introduction

Social aspects: Most LA countries have resources on Fe, Co (e.G. Cuba) or Ni but some of them also on rare earths (e.g. Brasil). These valuable raw material can be used for high quality permanent magnets. This increases the price per unit at least a factor 100. For developing but also for controlling such high quality permanent magnets equipment as well as know how is necessary. One of the important parts are here easy to handle magnetometers which allows the production of sufficient high magnetic fields. The here proposed project shall help to develop the knowledge on preparation of modern magnetic materials, on measuring technique of these materials as well as on characterization techniques. Additional to these technological aspects shall be mentioned that the education of academic members on an up to date physics is a contribution to the intellectual development of a country and therefore important.

High magnetic fields are necessary in order to perform several types of solid state experiments. In addition to magnetic materials, many high field experiments are also possible on several other classes of materials. Thus, experiments which need high magnetic fields cover areas from semiconductor physics (such as e.g. quantum dots), through superconductivity (organic superconductors, high T_c superconductors) and extending to magnetism (e.g. phase diagrams of rare earth-3d compounds, particularly those having high anisotropy fields (1), study of actinide compounds, molecular magnetism etc.). A comprehensive survey of applications of high magnetic fields was given in (2).

The present proposed network concentrates on training of researchers in the use of high field experiments for the study of various magnetic phenomena and advanced magnetic materials. Within the area of magnetism and magnetic materials many open questions still exist which need high magnetic field experiments to resolve satisfactorily. Examples include: field induced magnetism (as e.g.. in YCo₂ and similar compounds (3,4)), field induced changes of the spin structure (as e.g. in R₂Co₁₇ and R₂Fe₁₇ based materials (5)) but also problems which are related to the application of hard magnetic materials such as the study of magnetocrystalline anisotropy covering a broad temperature range (as e.g. in Sm₂Co₁₇ based permanent magnets (6), R₂Fe₁₄B-based permanent magnets (7), R(Fe,Ti)₁₂ alloys (8,9) and exchange coupled nanocomposite magnets (10)). In order to determine the anisotropy field directly, rather than by extrapolation, external fields at least of the same magnitude or higher are necessary (see also the SPD technique (11)).
In addition, at low temperatures, several fundamental aspects of magnetism can be investigated. Here, we enumerate a few interesting examples:

1. 
   The behaviour of isolated nanometric particles based on ferromagnetic elements such as Fe, Co or Ni. Small non-interacting particles can be described as superparamagnetic systems for which the ratio of magnetic to thermal energy determines the magnetization behaviour. This can be modelled by applying the usual theoretical framework for superparamagnetism. At very low temperatures, dipolar and also tunneling effects can affect the magnetization character. Here, the additional question of whether such small particles are still simple ferromagnets - especially at the surface - is of interest. High field magnetization measurements will shed further light on the nature of the phenomenon.
   

2. 
   Frustrated systems: Spin-glass like systems and superparamamgnetic clusters at low temperatures and high fields. The undefined ground state in such systems can lead to unexpected magnetization behaviour. High field magnetization experiments are a prerequisite for further study and will also facilitate measurements of the total moment of these clusters. For magnetic semiconductors in which these atoms are at random in the cation lattice, the material mainly shows, at low temperatures and low fields, superparamagnetic clusters and spin-glass form. The high magnetic field experiments will give information of the magnetic saturation field value as well as the total moment value of the magnetic matrix for these systems.
   

3. 
   Molecular Magnets. These types of materials have recently generated considerable interest. Molecular magnets can be isolated molecules (zero-dimensional) or those with extended bonding within chains (1D), within layers (2D) or within 3D network structures. Additionally, complexes exist involving 3d elements which undergo a temperature- or field-induced transition from a low spin to a high spin state. All these materials are either possible candidates for a new type of recording medium or of basic interest for a new family of magnetic materials.
   
4. 
   Doped magnetic semiconductor materials: Magnetic semiconductor materials at low and high applied magnetic fields. Compound semiconductor materials for which an appreciable fraction of the cations is atoms of iron, manganese or similar elements show interesting magnetic properties and all of these materials can be labelled magnetic semiconductors (MS). The particular magnetic behaviour occurring in any particular case depends to a large extent on the distribution of the magnetic atoms in the lattice.
   
5. 
   Investigation of magnetic phase diagrams: paramagnetic P, antiferromagnetic (AF) spin-flop (SF) and forced paramagnetic (FP) phases and P-AF, AF-SF and SF-FP transitions. Ordered systems: magnetic phase diagrams. For compounds, where the arrangement of magnetic atoms on the cation lattice is regular, the exchange interaction between these atoms is usually antiferromagnetic (AF) and, in the simplest case, collinear antiferromagnetic behavior occurs. However, for an antiferromagnetic material the field dependence of magnetization has to be distinguished for different ranges. For sufficiently low fields the magnetization of the AF ground state is proportional to the strength of the applied field. On the other hand, for sufficiently high fields, the magnetic moments are force to the paramagnetic region (P) in the phase diagram. Depending on magnetic anisotropy and the direction of the applied field an intermediate field strength can switch the magnetic moments into a direction perpendicular to the applied field giving rise to spin-flop (SP) behavior. In this SP phase the magnetization is also proportional to the applied field. Thus, low and high field magnetization experiments are needed to study the phase diagrams of these materials.
   

f) Exchange phenomena: Exchange interactions between localized moments of a magnetic matrix and bound holes (electrons): bound magnetic polarons (BMP’s). In these materials, BMPs can arise due to the presence of non-ionized acceptors or donors. They must have relatively high concentrations for the BMP effects to be observed, but not so high that impurity bands are formed. The bound hole (electron) interacts with the spins of the magnetic ions and tends to produce ferromagnetic alignment in those spins. Thus, in a simple model, the material can be considered as an irregular assembly of ferromagnetic spheres in a matrix which can be AF or P, depending upon the temperature, magnetic field conditions, etc. This behavior can be investigated by various types of magnetic measurements, the most common being measurements of magnetization as a function of magnetic field and measurements of magnetic susceptibility as a function of temperature.
g) Influence of extended structural disorder on magnetic intrinsic properties: studies of magnetic properties in magnetic materials are usually performed on the assumption of a perfect crystal structure. Yet, modern magnetic materials such as RE₂Co₁₇, RETM₁₂, RE₃TM₂₉ usually exhibit extended structural defects; in most cases, planar defects are the dominant type (13). Theoretical calculations normally ignore such disorder. Systematic experimental studies which correlate the occurrence of disorder with the magnetic properties are needed in order to obtain a solid experimental basis for explaining quantitatively the behaviour of intrinsic properties such as magnetocrystalline anisotropy and magnetostriction. Methods for the quantitative characterisation of planar defects have been recently developed (14) which, together with measurements at high magnetic fields, opens up the possibility of studying such correlations.

In order to characterize the magnetic state of such materials measurements of magnetization covering a broad temperature range (from very low up to elevated temperatures) are of prime importance. Additionally, other complementary magnetic techniques can be employed, including magneto-resistance, magnetostriction measurements and also magneto-optical investigations. For the study of magnetic phase diagrams, the pressure dependence is an important additional parameter.

The physical background to several of the problems outlined above will be taught in formal courses and in group research seminars and discussions at the participating host universities. Expertise in performing relevant key experiments and in solving such problems will be gained by the involvement of the trainees and exchange scientists in local projects in these subject areas at the host institutions. Furthermore, experience and training in the often difficult techniques of sample preparation will be obtained
2. Magnetisation measurements
Accurate and sensitive measurement of the magnetization in high magnetic fields, although difficult, is important in order to allow the investigation of systems with small magnetization values. Here, many improvements in the experimental techniques are still required. The grant holders will be trained in the construction and development of magnetisation measuring devices.
Pick-up systems
Generally, magnetisation is measured using a pick-up coil system, which has to be compensated in order to measure the magnetisation M rather than the inductance B. For this purpose, different arrangements of pick-up coils have been developed – see Fig.1. It has been found that the coaxial system, which is based on Maxwell coils, is the most suitable. (12). The main requirement for constructing a pick-up system is that the space distribution of the field H around the sample is developed into a dipole (and quadrupole) contribution. These contributions should be compensated in order to cancel the effect of the external field. Therefore, such systems consist of at least 2 coils (see Fig.1c). The induced voltages can be written as:

where u_i, N_i, K_i R_i (i= 1,2) are the induction voltage, number of windings, coupling factor and radius of the outer (i =1) and inner (i = 2) pick up coils, respectively.
Dipole compensation is fulfilled when R₁²N₁ = R₂²N₂ is valid. The coupling factor with respect to the field H is the same for both coils, but not with respect to the sample. It is assumed that, for the outer coil, the voltage due to the magnetisation can be neglected (actually, a small induced voltage exists due to M, which reduces only the calibration factor). Subtracting now the signal of the two anti-parallel wound coils causes a cancelling of the effect of the field – which yields the dipole-compensation. Also, higher order multi-poles can be compensated, which leads to a more complex pick-up system, for which more space is required. Therefore, for pulsed field systems, only the dipole compensation is normally used.

Fig.1: Scheme for a coaxial pick-up system for measuring the magnetization.

The sensitivity of a magnetization measurement system is limited by two factors. Most important is the residual imbalance in the pick-up system (also due to higher order) multipoles); it should be noted that for measurements on paramagnetic substances a compensation of 1 . 10⁶ is desired! Therefore such pick up system must be machined with an accuracy of m and, additionally, the windings must adhere exactly to the calculated parameters. The main problems in this respect are: a) it is very difficult to machine the insulating materials, on which such pick-up coils are wound, to within 1 m, and b) the wires leading from the pick-up system to the measuring electronics have to be twisted carefully in order to avoid areas where undefined induction voltages may arise.
Another major problem arises when temperature-dependent measurements are performed, because the degree of compensation depends sensitively on the position of the pick-up system with respect to the high field magnet. If the pick-up system is inside the furnace, a range of temperature rises can be generated within the different coils forming the pick-up system which can thus be subject to temperature gradients. This can also reduce the degree of compensation. Naturally this is not a problem for a magnet which delivers a large field homogeneity over an extended length – in this case the compensation is less affected by small variations of the position due to the thermal expansion. However, for a high field pulsed magnet, because of the limited energy, this is generally not possible: Additionally, the magnet deforms at high fields which causes a further reduction of the homogeneity. All these effects lead to a dramatic reduction of the achieved compensation with changing temperature. An additional problem is caused by the system noise, which increases with increasing maximum field of the system. The latter effect is caused mainly by vibrations in the high field magnet but also by noise in the field producing current. In metallic systems, eddy currents generated in the sample can also cause a measuring error. Thus, using an inductive pick-up system for temperature dependent magnetization measurements in a pulsed field of short duration, the maximum sensitivity is restricted to about 0.01 emu.

Additionally, it should be mentioned that the sensitivity depends directly on the coupling between the sample and the pick-up coil. For small samples or thin films it is very difficult to achieve a reasonable sensitivity.

Because the construction of well-balanced pick-up systems is the most important step defining the sensitivity of such high field magnetometers training will be given in the fabrication of various types of pick-up systems

3. Pressure dependence of magnetization

In order to undertake magnetization measurements as a function of the temperature at high pressures, the development of the following is proposed:

a) A pressure cell for external isostatic pressures up to 15 kbar for applications in pulsed field systems and inside which a pick-up system would be mounted. The outer diameter of the cell would be <12mm. Expertise in measurements in static fields at high pressures already exists at T.U.Vienna.

b) The Semiconductor Centre (Mérida, Venezuela) has the expertise in transport, optical and vibrational properties under very high pressure, and is interested to develop a diamond pressure-cell to be incorporated into the pick up coils of pulsed magnetic field systems. The physical background to the problems associated with designing and constructing such a system will be covered in the courses that will be offered within the programme and practical training in pressure technology. and in modern experimental techniques will be given.

4. Magnetostriction measurements.
Magnetostriction is an important intrinsic parameter of magnetic materials, which scales with temperature, similar to the magnetocrystalline anisotropy. Therefore, recently at T.U.Vienna, a program was initiated to measure this property on commercially available permanent magnets as well as on novel hard magnetic compounds, on which they are based. Because many of these samples have a large anisotropy, high external fields are necessary for saturation. The magnetostriction of rare earth containing materials in high fields can be measured using standard strain gauges. In these compounds the magnetostriction is of the order of 100 ppm which means that by using strain gauges - an easily achievable sensitivity of 1ppm is sufficient. In high field systems commercial strain gauges, from various suppliers (e.g. Hottinger, Micro-measurement etc.) and an ac-bridge with a sufficiently high carrier frequency (typically 50 kHz) can be used. Such an ac-bridge is favourable for noise suppression.

The physical background to magnetostriction and its effects will be included in the courses on magnetism that will be offered and also practical training in the use of modern techniques for measuring magnetostriction will be given.

5. Magneto-resistance
Magneto-resistance is a very important property both from the fundamental and applications viewpoints. Here, samples with a large magneto-resistance are of particular interest. From the experimental point of view, it is a very simple technique which can employ either d.c. or a.c. methods. In all cases, it needs a four contact sample holder (two for applying the current and two for getting the measuring voltage). The measurement should be performed with a bipolar pulsed field in order to correct for offset or drift voltages.

The physical background will be covered in the courses to be offered on magnetism and training given in the practical techniques for measuring magneto-resistance.

6. Magneto-optical properties

Magneto-optical properties are important for storage applications but also to investigate the band structure (under external field). This technique is very suited for use in pulsed high fields. Therefore optical properties, such as optical absorption (energy gap) in the temperature

range from 4 K to 300 K at normal pressure, optical absorption under pressure and lattice vibrations (Raman), will be studied. Additionally optical methods for measuring the hysteresis loop at the surface are of great interest – especially for thin films. Possibly such methods can be considered for pulsed field measurements.

Training in the use of techniques for studying magneto-optical properties will be given as part of the project work for students and researchers. This training will include problems associated with the introduction of new methods.

7. Data acquisition
The signals coming from each experiment are linked to a digital data acquisition system, consisting of a digital storage oscilloscope or a transient recorder, or similar and then they are transferred into a PC. Some data handling software is also necessary.
New methods for measuring the magnetisation (in pulsed high field systems) will be developed in order to increase the sensitivity of the pulsed field magnetometer.

Various courses, including practical exercises, will be offered as this is considered to be a very important aspect of modern experimental magnetism. Hence, there will be a strong emphasis on promulgating and broadening expertise within the partner groups in modern magnetic data acquisition.

8. Methods of increasing the sensitivity of magnetisation measurements
Up to now, mainly so-called “DC-methods” have been used for measuring the magnetisation Such a system simply integrates all the input. However, this tends to have high associated noise, which limits the achievable sensitivity. Therefore, it is proposed in the present study to employ methods for enhancing the signal to noise ratio, using a lock-in technique, and by improving the coupling between the sensor (i.e. the pick-up coil(s)) and the sample.
To increase the sensitivity, two different methods for measuring the magnetisation are proposed: a) vibrating sample (coil) technique and b) modulated field technique.

This work deals with modern measuring methods in physics which are based on good knowledge in electronic. There many physicist have not sufficient knowledge in this topic. Therefore the grant holders shall be trained on applying such methods within small projects on high field measuring problems.

8.1. Vibrating sample (coil) technique
The vibrating sample method is well established in static magnetometers. It has the advantage that, here also, the lock-in technique can be used, which gives an improved signal to noise ratio. There exists two possibilities to realise this method: i) vibration of the sample, ii) vibration of the pick-up coil(s). In the case of using small thin surface pick-up coils the second method may be advantageous. The pick-up coils deliver an ac-signal, which is proportional to the magnetisation. The advantage of this method compared with a modulation technique is that a piezo-electric actuator can be used in the cryostat directly. Therefore, its use should be much more straightforward. Additionally the effects of induction voltages resulting from non-ideal compensation can be suppressed because the frequency of the fundamental high field pulse is much lower than that of the induced voltage. Key questions here include:

(i) Is there any influence of the high magnetic field on the piezoelectric transducer?

(ii) Does the amplitude of the actuator change with field?

Also this is part of modern measuring methods including good knowledge in electronic – applying such methods in magnetism. Because here many physicist have not sufficient knowledge the grant holders will be motivated to improve and to apply such methods within small projects on high field measuring problems.

8.2. Modulated field technique
A similar effect can be achieved by modulating the field with a small periodic ac-field of a sufficiently high frequency. A lock-in technique can be used in this case for further amplification, which essentially improves the signal to noise ratio. However, the skin effect limits its reliability for metallic samples.

Also this work deals with modern measuring methods in physics which are based on good knowledge in electronic. There many physicist have not sufficient knowledge. Therefore the grant holders shall be trained on applying such methods within small projects on high field measuring problems.

9. Aims of the project

1. 
   Providing training of members (students, post docs and young scientists) of the partner laboratories ( or Facilitating mutual assistance between the partner laboratories in LA and in Europe) in constructing and installing high field systems and including modules for measurements at high pressures. Such modules will be developed during project work, which is part of the practical education. Learn to find good and reliable solutions for high field systems and measuring methods in these apparatus.
   
2. 
   Teach how to develop measurement methods for characterizing magnetic materials. This will mainly involve magnetization measurements, magneto-optical measurements but also, to a lesser extent, magnetostriction and magneto-resistance measurements. Systematic comparisons of measured properties for well defined materials between partner laboratories will be undertaken. Here the candidate shall learn to evaluate data critically. Students (graduate, post docs, young scientists) ) exchange between the groups is the basis of know how transfer between all involved institutions.
   
3. 
   Teach to learn how to handle problems, and their physical background, in the measurement of magnetization for various advanced and novel materials in pulsed fields, including:
   

1. 
   Electronic problems (integrator stability, digital integration procedures). The optimal method of integration will be determined. The integration of the signal (which is proportional to dH/dt as well as to dM/dt) can be performed using an analogue integrator or by an integration procedure supported by a digital computer. The required conditions for a reliable integration procedure shall be established. Here measuring electronic can be trained.
   
2. 
   Calibration problems. Identification of suitable calibration standards for a pulsed field magnetometer. Careful and critical thinking shall be trained.
   

Generally, the field calibration for a transient field can be performed with a coil having a well-defined effective cross sectional area (N.A_eff). Errors associated with the wires connecting the coil with the measuring system, as well as those related to the integrator constants (which are generally not accurately known), limit the reliability of this method. The use of Hall probes in pulsed fields is also possible; however, errors due to parasitic induction voltages, as well as time-limiting effects, have restricted their use. Therefore, field calibration (at room temperature) is performed using the internal anisotropy field for barium ferrite (H_A = 1.65T) measured by the SPD technique. This material is chosen because its value of H_A changes only very slightly around room temperature. Up to now, only data for the anisotropy field as published in the literature were used. Here, a careful comparison of a calibrated coil system with Hall probes, but also including a sample calibration, will be performed. A search for a better calibration procedure will be undertaken as an integral part of the partner groups’ collaborative projects on magnetic materials.

The magnetisation M is generally calibrated using the M(H) relationship for pure Ni and pure Fe. However, the effects of eddy currents in the sample limits the reliability of such a calibration procedure.

A non-conducting soft magnetic calibration material such as Fe₃O₄ is proposed since this has already employed successfully by T.U.Vienna. The problem here is that these materials exhibit a rather low Curie-temperature, and consequently the magnetization at room temperature exhibits a too high temperature dependence. Thus, here also, a better calibration standard needs to be identified –This will also be a topic for joint projects involving the grant holders.

4. 
   Samples to be used for the investigations include: Hard magnetic materials such as: ferrites, RE-Fe-B-based and Sm-Co-based alloys (including 1/5 and 2/17 type Sm-Co), plastic bonded and fully dense magnets. Additionally: nanocrystalline exchange-enhanced RE-Fe-B materials, including single phase and nanocomposite melt spun ribbons mechanically alloyed powder and sputtered monolithic and multi-layered thin films; heavy fermion systems, spin-glass systems, molecular magnet systems, magnetic semiconductors etc.
   

Training will be given in the important aspect of preparation and initial structural characterisation of good quality samples of the types enumerated above. This will be a good medium for education in state-of-the-art materials science and will be an essential element of the project in facilitating the provision of well-characterised samples for the other parts of the joint programme
10. Summary of training and education topics:

1. 
   High Field technology:
   

• 
  Construction and preparation of coils
  
• 
  Development of sensors
  
• 
  Calibration problems
  

2. 
   Measuring techniques for various aspects of magnetism:
   

• 
  Magnetisation
  
• 
  Magneto-optics
  
• 
  Magnetostriction
  
• 
  Anisotropy
  

3. 
   Pressure techniques
   
4. 
   Data acquisition
   
5. 
   Solid state physics especially:
   

• 
  Magnetism
  
• 
  Small particle physics
  
• 
  Phase transitions
  

6. 
   Materials preparation and synthesis, including:
   

• 
  Alloy preparation by arc melting and mechanical alloying
  
• 
  Chill block melt spinning of microcrystalline and nanocrystalline rare earth alloy ribbon samples
  
• 
  Preparation of polymer bonded and fully dense hot pressed and forged magnet samples from the above ribbon material
  
• 
  Preparation of monolithic and multilayered thin film rare earth transition metal alloy hard magnetic samples
  
• 
  Preparation of nanostructured hard magnetic ferrite powder and bulk samples
  
• 
  Structural and ‘microstructural’ characterisation of hard magnetic samples
  

Hence, in summary, training will be given in a very wide range of topics, ranging from physics to engineering, within this proposed project.

References
1) F.R.de Boer, Z.G.Zhao

Physica B 211 (1995) 81

2) MRS bulletin Vol XVIII (8) (1993) 17 - 63

3) S. Misawa

Physica B 211 (1995) 158

4) H.Yamada

Physica B 211 (1995) 161

5) S.Sinnema

Thesis „Magnetic Interaction in R₂T₁₇and R₂T₁₄B intermetallic compounds“

Univ. Amsterdam 1988

6) J.C.Tellez-Blanco, X.C.Kou, R.Grössinger, E.Estevez-Rams, J.Fidler, B.M.Ma

Proc. of 14th International Workshop on Rare-Earth Magnets and their Applications;

World Scientific Ed. F.P.Missel, V.Villas-Boas, H.R.Rechenberg, F.J.G.Landgraf

Sept. 1996 Sao Paulo Brasil p. 707 - 716

7) R. Grössinger, X.K. Sun, R. Eibler, K.H.J. Buschow, H. Kirchmayr

J. Physique 46 (1985) C6 - 221

8) X.C. Kou, T.S. Zhao, R. Grössinger, H. Kirchmayr, X. Li, F.R. de Boer

Phys. Rev. Vol. 47, No. 6 (1993) 3231 - 3242

9) R.Grössinger, X.C.Kou, G.Wiesinger

IEEE Trans. on Magn.30 (1994) 1018-1020

10) H.A.Davies

J Magn Magn Mater 157/158 (1996) 8

11) G.Asti, S.Rinaldi

J. Appl. Phys. 45 (1974) 3600

12) R.Gersdorf, F.A.Muller, L.W.Roeland

Col. Int. CNRS (1967) 166

13. 
    E. Estevez Rams, A. Penton, S. Novo, J. Fidler, J. C. Tellez-Blanco, R. Grossinger
    J. of Alloy and Compounds, 283 (1999) 289-295
    
14. 
    E. Estevez Rams, J. Martinez-Garcia, A. Penton Madrigal, R. Lora Serrano
    Phys. Rev. B, 63 (2001) 54109-54118
    

15) J. González, R. Rico, E. Calderón and M. Quintero, Absorption Edge of MnGa₂Se₄ Single Crystals under Hydrostatic Pressure, phys. stat. sol. (b) 221, 45-49 (1999)

16) M. Quintero, R. Brun Del Re and J. C. Woolley, Crystallogrphic Ordering and the Effects on Magnetic Susceptibility in Some Semiconductor Alloys of MnIII₂VI₄ Compounds, Phys. stat .sol., (a) 159, 361, (1997)

17) G. S. Porras, M. Quintero, R. Barrios, J. González and J. Ruiz, Electrical Properties of the Cu₂FeGeSe₄ compound, phys. stat. sol. (b) 215, 1067 (1999)

18) E. Quintero, R. Tovar, M. Quintero, J. González, J. Ruiz, P. Bocaranda, J. M. Broto, H. Rakoto and R. Barbaste, Magnetic Behaviour of Cu₂FeGeSe₄, J. Mag. Mag. Mat. 210, 208-214 (2000)

19) M. Quintero, R. Tovar, A. Barreto, E. Quintero, J. González, G. Sánchez Porras, J. Ruiz, P. Bocaranda, J. M. Broto, H. Rakoto and R. Barbaste, Crystallographic and Magnetic Properties of Cu₂FeGeSe₄ and Cu₂FeGeTe₄ Compounds, Phys. Stat. sol. (b) 209, 135 (1998)

20)M. Quintero, R. Cadenas, R. Tovar, E. Quintero, J Gonzalez, J. Ruiz, J.C. Woolley, G. Lamarche, A-M. Lamarche, J.M. Broto, H. Rakoto, R. Barbaste Magnetic spin-flop and magnetic saturation in Ag₂FeGeSe₄, Ag₂FeSiSe₄ and Cu₂MnGeSe₄ semiconductor compounds, Physica B 294-295 (2001) 471-474

Partners:
Europe:

1. 
   Prof. Roland Grössinger, T.U.Vienna, Austria (coordinator) (TUV)
   
2. 
   Dr. JM Broto , LNCMP. Toulouse, France (LNCMP)
   
3. 
   Prof. Hywel Davies and Prof Mike Gibbs, Univ. Sheffield, U.K. (US)
   

Latin America

4. 
   Prof. Joao Paulo Sinnecker, Univ. Rio de Janeiro, Brazil (UR)
   

1. 
   Prof. Ernesto Estevez-Rams, Univ. Havana, Cuba (UH)
   

5. 
   Prof. Vicente Sagredo + Prof. Gonzales, Univ de los Andes, Venezuela (UV)
   
6. 
   Prof Hector Bertorello, Univ Cordoba, Argentina (UC)
   
7. 
   Dr.Jose Matutes , Centro de Investigacions en Materiales Avanzados; Mexico (IM)
   

Running time of the project: 3 years.
Costs of the project: 321.350.- EURO (EC contribution) – the costs are determined by grants, by professors visits and by summer- respectively winter-scools. This means that the total costs are of the order of at least 420.000.-- EURO.
Coordinator: ROLAND GROESSINGER, TUV
Austria

R.Grössinger, R.Sato

Inst.f. Festkörperphysik, T.U.Vienna

Wiedner Hauptstr. 8 – 10

A-1040 Austria

Tel: [phone] - 13150

FAX: [phone] - 13199

e-mail: [e-mail]

http://www.ifp.tuwien.ac.at/

France

Prof. JM Broto

LNCMP143 av de Rangueil

31432 TOULOUSE CEDEX4

TEl: [phone]

FAX: [phone]

e-mail:

http://www.ups-tlse.fr/
Great Britain
Prof H.A.Davies, Prof M.R.J.Gibbs,

Centre for Advanced Magnetic Materials and Devices

Departments of Engineering Materials (HAD) and of Physics and Astronomy (MRJG)

University of Sheffield

Sheffield S1 3JD

U.K.

Tel: [phone] (HAD), [phone] (MRJG)

Fax: [phone] (HAD), [phone] (MRJG)

Email: [e-mail] [e-mail]

http://www.shef.ac.uk/materials/index.html

Brazil

Prof Joao Paulo Sinnecker

Instituto de Física - UFRJ

CP 68528

21945-970 Rio de Janeiro, RJ, BRASIL

Tel: [phone]

FAX: [phone]

e-mail: [e-mail]

http://www.if.ufrj.br/
Cuba:
E. Estevez-Rams

Instituto de Materiales y Reactivos. Universidad de la Habana

San Lazaro y L. CP 10400

C. Habana. Cuba

Tel: [phone]

FAX: [phone]

e-mail: [e-mail], [e-mail]

web-adress: imre.oc.uh.cu

Venezuela:

Prof. Dr. Jesus Gonzales ( Director del Centro de Estudios de Semiconductores)

Centro de Estudios de Semiconductores

Departamento de Fisica

Facultad de Ciencias, Nucleo La Hechicera

Universidad de Los Andes, Merida, Venezuela

Tel: [phone]

FAX: [phone]

e-mail: JESUS GONZALEZ [e-mail]

Prof,. Sagredo

Physics Department

Facultad de Ciencias

Universidad de los Andes

Mérida,Venezuela

Fax: [phone]

e-mail: "Vicente Sagredo" [e-mail]

Argentina:
Prof Hector Bertorello,

Univ Nacional de Cordoba, Argentina

Adress: Medina Allende y Haya de La Torre

Cuidade Universitaria

5000-CORDOBA-ARGENTINA

Tel: [phone]

FAX: [phone]

e-mail: [e-mail]

Mexico:
Dr. José Matutes

Centro de Investigacions en Materiales Avanzados

Jefe de Depto. De Materiales Ceramicos, Chihuahua

Complejo Industrial Chihuahua

Miguel de Cervantes, 120

31109 Chihuahua, Mexico

Tel: 391 104

FAX: 391 112

e-mail: [e-mail]

http://www.shef.ac.uk/materials/index.html
Events :
Summer school in Mexico (Chihuahua) from 5th to 8th April
“Advanced materials in high magnetic fields”

Agenda

5th April
9-10: Check-in

10 -10:30 Wellcome by local authorities

10:30 – 11: Presentation of general idea and targets of the project “ Measurement methods involving high magnetic fields for advanced and novel materials” (R.Grössinger T.U.Vienna)

11-11:30 Coffee Break

11:30 – 12:30 Organization and financial aspects of the project (O.Mayerhofer T.U.Vienna)

12:30 – 14 Lunch

Presentation of laboratory facilities of each participant – 20 minutes.

14 – 15:40

Dr.Jose Matutes , Centro de Investigacions en Materiales Avanzados; Mexico

Prof. Vicente Sagredo + Prof. Gonzales, Univ de los Andes, Venezuela (UV)

Prof. Joao Paulo Sinnecker, Univ. Rio de Janeiro, Brazil (UR)

Prof. Ernesto Estevez-Rams, Univ. Havana, Cuba (UH)

Prof. Hector Bertorello, Univ Cordoba, Argentina (UC)

15:40 – 16 Coffe break

16-17

Dr. JM Broto , LNCMP. Toulouse, France (LNCMP)

Prof. Hywel Davies and Prof Mike Gibbs, Univ. Sheffield, U.K. (US)

Prof. Roland Grössinger, T.U.Vienna, Austria (TUV)

19-… Dinner
6^th April

Advanced Materials – here some laboratories shall give an overview of materials which are of interest within our project.

10-10:30 Prof. Hywel Davies

10:30-11:10 Prof. Gonzales + Prof. Vicente Sagredo

11:10-11 :30 coffee break

11 :30 – 12  Prof. Hector Bertorello

12 – 13:30 Lunch

Characterization of materials

13:30 – 14 Prof. Ernesto Estevez-Rams

14 – 14:30 Prof. Joao Paulo Sinnecker

High magnetic fields – generation - application

14:30 –15 Dr. JM Broto

15 – 15:30 Prof. R. Grössinger

15:30 – 16:00 Dr.Jose Matutes

16-16 :30 Coffe break

16 :30 – 18 :00 Discssuin about the further organization of the project
20 Dinner
7th April (or some other day)

Two invited tutorial talks (speakers?)

1. 
   High magnetic fields
   
2. 
   New advanced magnetic materials
   

Summer School Toulouse (France) in July 2003

Proposed title: “High field technology”

ALFA II Application Form– Sub-Programme B Project