Talk 1: Advanced MTJ and CPP-GMR devices using Heusler alloys for magnetic memory and data storage
Dr. Zhenchao Wen. Assistant professor, Institute for Materials Research and Center for Spintronics Research Network (CSRN), Tohoku University

Remarkable magnetic and spin-dependent transport properties arise from well-designed materials and heterostructures. Half-metallic Heusler alloys with high spin polarization exhibit properties that are particularly advantageous for the development of high-performance spintronic devices. In this talk, the speaker will introduce magnetic tunnel junctions (MTJs) and current-perpendicular-to-the-plane giant magnetoresistance (CPP-GMR) devices using half-metallic Heusler alloys for magnetic memory, spin MOSFET, and data storage. Firstly, MTJs with Co₂FeAl Heusler alloy films will be introduced with the discussion of tunneling magnetoresistance (TMR), spin-transfer torque (STT) induced magnetization switching, interfacial perpendicular magnetic anisotropy (PMA), and voltage control of magnetic anisotropy (VCMA). Secondly, CPP-GMR devices using half metallic Heusler alloy will be discussed. Especially, a large CPP-GMR ratio with a low junction resistance was achieved in nanojunctions with Co₂(Fe, Mn)Si electrodes and a Ag spacer, which could satisfy the application of read sensors for hard disk drives (HDDs) for ultrahigh density magnetic recording of more than 5 Tbit/inch².

Brief CV:

Zhenchao Wen got his PhD from Institute of Physics, Chinese Academy of Sciences (IOP-CAS) in 2010. He worked as a research associate in National Institute for Materials Science (NIMS), Japan, from 2010 to 2015, then he moved to Tohoku University and was promoted to be an assistant professor in 2016. Dr. Wen has more than 10 years’ research experience in spintronics. Especially, his researches are focused on magnetic tunnel junctions (MTJs) for magnetic random access memories (MRAMs) and spin MOSFET devices, as well as current-perpendicular-to-the-plane giant magnetoresistance (CPP-GMR) for hard disk drives (HDDs) for ultrahigh-density magnetic recording. To date, he has published more than 60 peer-reviewed papers and 13 patents. He is also a reviewer for more than 10 scientific journals.

Talk 2: Manipulation of spin current in antiferromagnetic insulators

Dr. Dazhi Hou, Assistant professor, WPI Advanced Institute for Materials Research, Tohoku University

Effective spin current manipulation is the key process to realize the spin-based transistor and unfortunately proved to be quite challenging in the electron-based spin channels, in which the propagation of spin current relies on the isotropic electron diffusion. Recent works show that spin can transmit through antiferromagnetic insulators [1,2], in which itinerant electrons cannot pass, indicating alternative methods for spin manipulation. In this talk, the speaker will introduce their recent progress in the effective manipulation of spin current in antiferromagnetic insulator with the methods different from those in conductive materials. The spin current switching by the phase and magnetic structure control will be discussed, with the introduction of two novel concepts: spin colossal magnetoresistance and nematic spin transmission in antiferromagnetic insulator[3-6]. These findings pave the road towards antiferromagnetic-insulator-based spin transistor and memory.

[1] C. Hahn et al., EPL (Europhysics Letters) 108, 57005 (2014).
[2] H. Wang, C. Du, P. C. Hammel, and F. Yang, Physical review letters 113, 97202 (2014)
[3] Zhiyong Qiu, Jia Li, Dazhi Hou* et al., Spin-current probe for phase transition in an insulator. Nature Communications 7, 12670 (2016).
[4] Zhiyong Qiu, Dazhi Hou* et al., accepted by Nature Materials.
[5] Dazhi Hou et al., under review
[6] Dazhi Hou. et al., Physical Review Letters 118, 147202 (2017).