Nanoelectronics Spin-caloritronics in magnetic tunnel junction nanodevices

Spin-caloritronics [1] is a new emerging research field combining Spintronics (spin transport electronics) and Thermoelectricity (heat transport electronics) in magnetic nanostructured systems. At such a scale, thermal gradients can play an active role to control and manipulate spin-based effects enabling the generation of thermally induced spin currents [2,3] or even thermally driven magnetization reversal [4]. Such effects are very promising as they would allow to improve energy efficiency in future ICT (information and communication technology) devices. However, most of these novel concepts still need to be addressed and studied experimentally.

The aim of the European JRP SpinCal project is to understand, quantify, control and optimize spin-caloritronic effects in different magnetic nanosystems to evaluate their efficiency for future R&D applications.

Our work in this project is focused on: a) Developing novel MTJ stacks for future thermoelectric applications b.) Studying thermal gradient effects on MTJ magnetization dynamics.

This approach is based on recently observed large tunneling magneto Seebeck ratios in magnetic tunnel junction (MTJ) structures [5, 6, 7], suggesting the potentiality of such devices, not only for magnetic random access memory (MRAM) devices or Spin Transfer Torque Nano-oscillators (STNOs), but also for on-chip energy harvesting applications. On the other hand, we believe that the exploration of heat driven magnetization dynamics could enable a better comprehension of Spin Transfer Torque (STT) magnetization dynamic phenomena in MTJ nanodevices and the contribution of heat, charge and spin currents at such conditions.

JRP SpinCal project partners Physikalisch-Technischen Bundesanstalt (PTB), Germany; National Physical Laboratory (NPL), UK; Istituto Nazionale di Recerca Metrologica (INRIM), Italy; University of Bielefeld, Germany; Cambridge University, UK; International Iberian Nanotechnology Laboratory (INL), Portugal; Institute of Physics of Czech Republic (FZU), Czech Republic.


Figure 1: a.) Tunnel Magneto-Resistance (TMR) and b.) Tunnel Magneto-Seebeck (TMS) voltage loops for easy axis magnetic fields. Blue and black arrows indicate the orientation of the pinned layer (PL) and free layer (FL) magnetization respectively. c.) Heat Power dependence of the TMS voltage for antiparallel (AP) and parallel (P) magnetic configuration of the MJ. Inset shows a sketch of the experimental setup (see ref. [5] for detailed explanation). Temperature profile through d.) the MTJ device and e.) the MgO barrier (see ref. [7])

Further enquires for this project can be directed to Santiago Serrano-Guisan:

[1] G. E. W. Bauer, A. H. MacDonald and S. Maekawa, Solid State Commun. 150, 459 (2010); G. E. W. Bauer, E. Saitoh and B. J. van Wees, Nat. Mater. 11, 391 (2012)

[2] K. Uchida et al., Nature 455, 778 (2008) ; C. M. Jaworski et al., Nat. Mater. 9, 898 (2010) ; K. Uchida et al., Nat. Mater. 9, 894 (2010)

[3] J-C. Le Breton, S. Sharma, H. Saito, S. Yuasa and R. Jansen, Nature 475, 82 (2011)

[4] M. Hatami et al., Phys. Rev. B 79, 174426 (2009) ; X. Jia et al., Phys, Rev. Lett. 107, 176603 (2011)

[5] N. Liebing, S. Serrano-Guisan, K. Rott, G. Reiss, J. Langer, B. Ocker and H.W. Schumacher, Phys. Rerv. Lett. 107, 177201 (2011)

[6] Walter et al., Nat. Mater. 10, 742 (2011)

[7] N. Liebing, S. Serrano-Guisan, K. Rott, G. Reiss, J. Langer, B. Ocker and H.W. Schumacher, J. Appl.. Phys. 111, 07C520 (2012)