Unusual behavior of coercivity in Hf/GdFeCo bilayer with MgO cap layer by electric current

• Published in: AIP advances Vol. 10; no. 10; pp. 105202 - 105202-5
• Main Authors: Hai, Ngo Trong, Kindiak, Ivan, Yurlov, Vladislav, Chandra Bhatt, Ramesh, Liao, Chun-Ming, Ye, Lin-Xiu, Wu, Te-ho, Zvezdin, K. A., Wu, Jong-Ching
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.10.2020; AIP Publishing LLC
• Subjects: Coercivity; Electric currents; Ferrimagnetism; Hall effect; High temperature effects; Low currents; Magnesium oxide; Ohmic dissipation; Resistance heating; Transition metals
• DOI: 10.1063/5.0023636
• ISSN: 2158-3226

We investigate the Hf/GdFeCo bilayer with the MgO cap layer for both rare earth (RE)-rich and transition metal (TM)-rich configurations of the ferrimagnetic sublattice in the presence of the perpendicular field. We study the coercivity using the anomalous Hall effect (AHE) technique by multiple measurements on the same sample. In the first set of measurements and at low electric currents, coercivity sharply drops because of the oxygen diffusion at the interface between MgO and GdFeCo when the AHE probe current is applied. During the subsequent measurements on the RE-rich sample, we observe a moderate decrease in coercivity at low currents and the coercivity increases in a high current range. Such nonlinear dependence of coercivity on electric current can be explained by the competing interplay of the spin–orbit torque (SOT) and the Joule heating effects. On the other hand, for the TM-rich case, the SOT effect is observed over a widely applied current range.