Field-angle and DC-bias dependence of spin-torque diode in giant magnetoresistive microstripe

摘要

The spin torque diode effect in all metal spintronic devices has been proposed as a microwave detector with a high power limit and resistivity to breakdown. The previous works have revealed the field-angle dependence of the rectified DC voltage (V_(DC)) in the ferromagnetic stripe. The giant magnetoresistive (GMR) microstripe exhibits higher sensitivity compared with the ferromagnetic stripe. However, the influence of the magnetic field direction and bias current in the spin rectification of GMR microstripe is not yet reported. In this work, the angular dependence and bias dependence of resonant frequency (f_R) and V_(DC) a*6 investigated. A macrospin model concerning the contribution of magnetic field, shape anisotropy, and unidirectional anisotropy is engaged to interpret the experimental data.f_R exhibits a |sin δ_H|dependence on the in-plane field angle (δ_H). V_(DC) presents either |sin δ_H| or |sin2 δ_H cos δ_H | relation, depending on the magnitude of H_(ext). Optimized V_(DC) of 24 μV is achieved under 4mT magnetic field applied at δ_H=170°. Under out-of-plane magnetic field, f_R shows a cos 2θ_H reliance on the polar angle (θ_H), whereas V_(DC) is sin θ_H dependent. The Oersted field of the DC bias current (I_(DC)) modifies the effective field, resulting in shifted f_R. Enhanced V_(DC) with increasing I_(DC) is attributed to the elevated contribution of spin-transfer torque. Maximum V_(DC) of 35.2 μV is achieved, corresponding to 47% increase compared with the optimized value under zero bias. Higher I_(DC) also results in enlarged damping parameter in the free layer, resulting in increased linewidth in the spin torque diode spectra. This work experimentally and analytically reveals the angular dependence of f_R and V_(DC) in the GMR microstripe. The results further demonstrate a highly tunable f_R and optimized V_(DC) by bias current without the external magnetic field. GMR microstripe holds promise for application as a high-power, frequency-tunable microwave detector that works under small or zero magnetic field.