Aisha Aqeel
Spin transport using magnetic insulators has recently attracted much attention to explore new functions in spintronics. To understand the spin transport at the interface between a normal metal (NM) and a ferromagnetic insulator (FMI), researchers have performed several experiments, including the spin Seebeck effect (SSE) and spin Hall magnetoresistance (SMR), mainly in collinear magnetic insulators such as the prototype yttrium-iron-granate (YIG). However, the sensitivity and response of these effects in noncollinear magnetic insulators are unknown. Here, we report the simultaneous detection of SMR and SSE in a noncollinear CoCr2O4 magnetic insulator using a locking detection technique [1,2].
For SMR detection, an alternating current is passed through the Pt Hall beam, causing spin accumulation at the Pt/FMI interface due to the spin-Hall effect. This spin accumulation is absorbed or reflected, depending on the direction of magnetization of the IMF. In addition, when a charge current flows through the Pt-Hall bar, it generates Joule heating, creating a thermal gradient at the Pt/FMI interface. This thermal gradient can cause thermal magnons in the CCO magnetic insulator, resulting in a spin current that is pumped into the Pt and can be electrically detected with ISHE. CoCr2O4 is a spinel with a collinear ferrimagnetic state below Tc = 94 K and noncollinear magnetic phases at lower temperatures. We studied the SMR and SSE at different temperatures (5K-300K). We observed a significant increase in the SMR and SSE at low temperatures, showing an enormous sensitivity to the noncollinear phases of the CoCr2O4 [2].
[2] A. Aqeel, Phys. Rev. B 92 (22), 224410 (2015)