# Spin caloritronics in metallic, insulating, and two-dimensional van der Waals materials

#### Dr Fasil Kidane Dejene, Loughborough University. Part of the condensed matter seminar series.

Dr Fasil Kidane Dejene, Department of Physics, Loughborough University, will be presenting a seminar on his research. All are welcome to attend.

The interaction between charge, spin and heat currents is investigated in spin-caloritronics [1] -- a merger of thermoelectrics (coupling between charge and heat) and spintronics (coupling between charge and spin). In this talk, I will first describe the Seebeck, Peltier and Nernst effects and discuss how they can be used to locally cool devices, probe phase transitions and changes in Fermi surfaces [2].

Next, I will introduce local and nonlocal spintronic device architectures that allow studying pure spin current and spin-polarized transport [3]. In such devices, unwanted Joule heating, due to the flow of electrons, is often considered a nuisance for functional spintronic device applications. However, the excess heat can be used in heat-assisted magnetic recording applications with improved areal density of magnetic data storage [4]. In the last part of my talk, I present alternative routes of utilising excess heat dissipation for spin caloric device applications. Using proof-of-concept spin-caloritronic device architectures in metallic and insulating systems, I will show that the flow of heat through a ferromagnet can drive an electronic spin current, an effect dubbed spin (dependent) Seebeck effect[5].

The Onsager-reciprocal process called the spin (dependent) Peltier effect results in the heating/cooling of a nanomagnet by the flow of a spin current [6]. I will also highlight the important differences with collective magnonic heat-spin related phenomena that are mostly present in insulating magnetic systems. Finally, I show the possibility of controlling the flow of heat using a magnetic heat valves that works exactly as GMR devices, but in the heat sector [5]. 1. Bauer, Solid State Communications 150 (11–12): 459–60, (2010). 2. Rana et al., Nano Letters, Accepted, (2018). 3. Dejene et al., Phys. Rev. B 91 (10): 100404, (2015). 4. Kryder et al., Proceedings of the IEEE 96 (11): 1810–35., (2008). 5. Dejene et al., Nature Physics 9 (10): 636–639, (2013). 6. Flipse et al., Nature Nanotechnology 7 (3): 166–168, (2012) For more details please contact Dr Satoshi Sasaki (S.Sasaki@leeds.ac.uk)

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