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Thermostable Spin Valves


Development of NiMn Spin Valves with Improved Exchange Field and Higher Thermal Stability

Tech Area / Field

  • PHY-SSP/Solid State Physics/Physics
  • INF-SIG/Sensors and Signal Processing/Information and Communications

3 Approved without Funding

Registration date

Leading Institute
Yerevan State University, Armenia, Yerevan

Supporting institutes

  • A.I. Alikhanyan National Science Laboratory, Armenia, Yerevan\nInstitute of Radiophysics and Electronics, Armenia, Ashtarak-2


  • CNRS / Institut de Physique et Chimie des Materiaux de Strasbourg, France, Strasbourg\nNVE Corporation, USA, MN, Eden Prairie\nPolytechnic University of Valencia, Spain, Valencia\n[Individual specialist]\nUS Department of Commerce / National Institute of Standards and Technology, USA, MD, Gaithersburg

Project summary

The thermal reliability of magnetic recording sensors is of increasing concern due to the high operating temperature in the sensor stripe as results of high bias current and small transducer size to maintain adequate signal level for high areal density. Although the NiMn-based spin valve has advantage of maintaining antiferromagnetic (AFM) coupling at much higher temperature (~380oC) than most other AFM materials, it is necessary to understand its thermal reliability limit and the mechanism affecting this limit in order to fully utilize it. Nevertheless, there has been few, if any, published research on the thermal reliability of spin valves sensors.

The blocking temperature TB of NiMn spin valve is primarily determined by the NiFe layer’s ferromagnetic properties since the Néel temperature for NiMn is far above the blocking temperature, unlike the other materials which have lower TN. This means, that for NiMn spin valve with the increase of the temperature the decrease of the exchange field starts much earlier than Tc of NiFe, i.e. exists the “ blocking temperature reserve”. Obviously that non-utilized reserve must be investigated and ways of using it for improving the exchange coupling field of ferro-antiferromagnetic layers should be found.

Our purpose is to improve the thermal stability and to increase the blocking temperature by alloying of antiferromagnetic NiMn layer by Ti.

The aim of Project

Increasing the exchange bias field and blocking temperature permit to obtain improved thermal stabile spin valves for use the sensor element in hard disk drives at elevated temperatures more than 200oC, particularly in automotive and aerospace applications.

Expected Results and Their Application

The investigations within the realm of this Project are in the field of applied research. During the realization of the Project the following aims will be achieved:

  • Achievement of antiferromagnetic θ-NiMn1-xTix as-deposited films.
  • Increasing the pinning field.
  • Increasing the blocking temperature.
  • Thermal stability of exchange coupling field above 200oC.
  • The decrease of the slope of the giant magnetoresistance temperature dependence.
  • The correlation the ordering factor of the antiferromagnetic layer to the exchange field.


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