Isotropic spin polarization in Heusler Co2FeAl thin films

Qinwu Gao,Yilin Zhang,Qi Liu,Jian Tu,Meiyang Ma,Pengfei Yan,Zhendong Chen,Yizhe Sun,Xuezhong Ruan,Liang He,Jiai Ning,Xianyang Lu,Ruifeng Wang,Zhihao Li,Yongbing Xu,Yu Yan

doi:10.1063/5.0076246

Abstract

Spin polarization and the Gilbert damping, as the two key parameters of the magnetic materials for spintronic applications, were suggested to be inversely proportional to each other in a series of Heusler alloys. Recently, large anisotropic Gilbert damping was found in Co2FeAl thin films, implying that spin polarization may be also anisotropic. Here, we report an isotropic spin polarization with a constant value of 60% in a 20-nm Co2FeAl thin film with a B2 structure, using spin- and angle-resolved photoemission spectroscopy and time-resolved magneto-optical Kerr effect. Furthermore, this result was also supported by the ab initio calculations that the difference of the spin polarization between all the orientations is less than 1% for the Co2FeAl thin film. This finding provides profound insight into the spin polarization in Co2FeAl alloys.

Highlights

Half-metallic Heusler alloys Co2FeAl have shown remarkable potential in spintronics1–5 due to their high Curie temperature,6 high magnetization,7,8 and low Gilbert damping constant.9 high spin polarization at room temperature is suitable for spin injection, spin filtering, and spin-transfer torque devices.1,10,11 Recently, the intrinsic anisotropic Gilbert damping has been observed in the Co2FeAl films.12 several groups proposed that spin polarization is linked to the inverse of the Gilbert damping.13,14 This might mean that anisotropic spin polarization can be observed in the Co2FeAl films
After a concise characterization of their structure and fundamental properties, the high spin polarization of 60% was observed in the Co2FeAl thin film for the easy magnetization axes using the spin- and angle-resolved photoemission spectroscopy (Spin-ARPES)
For the directions between the [110] and [110], the isotropic spin polarization can be evidenced by the constant demagnetization time measured by the time-resolved magneto-optical Kerr effect (Tr-MOKE), which is consistent with the ab initio electronic structure calculations

Summary

INTRODUCTION

Half-metallic Heusler alloys Co2FeAl have shown remarkable potential in spintronics due to their high Curie temperature, high magnetization, and low Gilbert damping constant. high spin polarization at room temperature is suitable for spin injection, spin filtering, and spin-transfer torque devices. Recently, the intrinsic anisotropic Gilbert damping has been observed in the Co2FeAl films. several groups proposed that spin polarization is linked to the inverse of the Gilbert damping. This might mean that anisotropic spin polarization can be observed in the Co2FeAl films. The intrinsic anisotropic Gilbert damping has been observed in the Co2FeAl films.. Several groups proposed that spin polarization is linked to the inverse of the Gilbert damping.. Several groups proposed that spin polarization is linked to the inverse of the Gilbert damping.13,14 This might mean that anisotropic spin polarization can be observed in the Co2FeAl films. After a concise characterization of their structure and fundamental properties, the high spin polarization of 60% was observed in the Co2FeAl thin film for the easy magnetization axes using the spin- and angle-resolved photoemission spectroscopy (Spin-ARPES). For the directions between the [110] and [110], the isotropic spin polarization can be evidenced by the constant demagnetization time measured by the time-resolved magneto-optical Kerr effect (Tr-MOKE), which is consistent with the ab initio electronic structure calculations. This work provides detailed information on the properties of spin polarization along various orientations

AND DISCUSSION

Findings

CONCLUSION