NiSi: A New Venue for Antiferromagnetic Spintronics*

Antiferromagnetic system is argued to provide a superior platform for the spintronic application than ferromagnetic compound. The strong exchange coupling in an antiferromagnet enhances the characteristic frequency for spin dynamics, thus making it faster in magnetic switching and more robust against external magnetic field perturbations. Recently, we have discovered antiferromagnetic order in single crystal nickel monosilicide (NiSi) with a Neel temperature of T_N > 700 K. Despite the wide application of nickel silicide in field effect transistors and nanoelectronic devices, magnetism was never detected in these systems. The magnetic characteristics of single crystal NiSi are investigated using elastic neutron scattering measurements on CORELLI and TRIAX spectrometers at ORNL and MURR, respectively. Magnetic structure refinement in conjunction with magnetic symmetry analysis reveals a non-centrosymmetric antiferromagnetic order with two independent noncollinear Ni moments of ~ 1.6 μ_B and 1.2 μ_B in the magnetic unit cell, canting out from the [111] diagonal plane. In addition, a small non-compensated moment in the a-c plane is also detected, which leads to a remarkable one-step switching transition for magnetic field application along the b direction at H ~ 900 Oe in magnetic hysteresis measurements. The one-step switching persists to high temperatures, making it an attractive candidate for spintronic application. Further insight into the electronic nature of the magnetic transition is obtained by performing magnetoresistance measurements in Hall configuration. We found that NiSi manifests significant magneto-electronic hysteresis effects in the Hall resistance R_xy, which can be related to metamagnetic switching phenomena between non-collinear spin configurations. Cumulatively, these properties underscore the importance of NiSi in the pursuit of antiferromagnetic spintronics.