Oral
03 Nov 2023
Antiferromagnets have attracted considerable attention due to their promissing properties such as the absence of stray field and the potential for ultrafast switching. Recent advancements revealed non-zero spin polarization in non-collinear antiferromagnets, enabling fabrication of Magnetic Tunnel Junctions (MTJs) with antiferromagnetic electrodes[1,2]. The investigation of voltage-controlled magnetic anisotropy (VCMA) in antiferromagnets has gained interest, with theoretical calculations on VCMA effect in PtMn[3-5]. In our study, we fabricated antiferromagnetic MTJs using PtxMn1-x as one of the electrodes. Fig. 1 shows TMR curves measured at various voltages on an MTJ with an antiferromagnetic layer (Buffer\CoFeB\MgO\PtMn\Capping). Sharp switching in Fig. 1a corresponds to CoFeB layer switching, disappearing with increasing bias voltage. In Fig. 1b, the magnetic signal at a larger magnetic field arises from changes in antiferromagnet's magnetic orientation, with stronger signals at higher voltages. To address Joule heating, measurements were conducted at a similar negative and positive voltage values (Fig. 1c). Positive voltage data (Fig. 1c Black) exhibited a TMR signal ten times higher than negative voltage data (Fig. 1c Red), indicating minor role of Joule heating. Signals above 50 Oe originate from magnetic orientation of PtxMn1-x electrode, suggesting voltage-controlled magnetic anisotropy and/or spin-polarization of PtxMn1-x plays an important role. We investigated a different structure (Buffer\CoFeB\MgO\PtMn\CoFeB\Capping) where sharp switching similar to tunneling anisotropic magnetoresistance based on exchange spring effect[6] was observed (Fig. 2a). Interestingly, TMR changes sign above 200 mV (Fig. 2b), different from MTJs based on IrMn. These results enhance understanding of antiferromagnetic systems and provide insights for advanced spintronics devices. Supported by the National Science Foundation.References: X. Chen, T. Higo and K. Tanaka, Nature, Vol. 613, p.490 (2023) P. Qin, H. Yan and X.Wang, Nature, Vol. 613, p.485 (2023) R. Cheng and Q. Niu, Phys. Rev. B - Condens. Matter Mater. Phys., Vol. 89, p.1 (2014) Y. Su, M. Li and J. Zhang, J. Magn. Magn. Mater., Vol. 505, p.166758 (2020) P.-H. Chang, W. Fang and T. Ozaki, Phys. Rev. Mater., Vol. 5, p.54406 (2021) B. G. Park, J. Wunderlich and X. Martí, Nat. Mater., Vol. 10, p.347 (2011)
