Komesu Takashi, Echtenkamp Will, Binek Christian, Dowben Peter A
Department of Physics and Astronomy and the Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Jorgensen Hall 855 North 16th Street, Lincoln, NE 68588-0299, United States of America.
J Phys Condens Matter. 2023 Apr 12;35(27). doi: 10.1088/1361-648X/acc710.
While induced spin polarization of a palladium (Pd) overlayer on antiferromagnetic and magneto-electric CrO(0001) is possible because of the boundary polarization at the CrO(0001), in the single domain state, the Pd thin film appears to be ferromagnetic on its own, likely as a result of strain. In the conduction band, we find the experimental evidence of ferromagnetic spin polarized in Pd thin films on a CrO(0001) single crystal, especially in the thin limit, Pd thickness of around 1-4 nm. Indeed there is significant spin polarization in 10 Å thick Pd films on CrO(0001) at 310 K, i.e. above the Néel temperature of bulk CrO. While CrO(0001) has surface moments that tend to align along the surface normal, for Pd on CrO, the spin polarization contains an in-plane component. Strain in the Pd adlayer on CrO(0001) appears correlated to the spin polarization measured in spin polarized inverse photoemission spectroscopy. Further evidence for magnetization of Pd on CrOis provided by measurement of the exchange bias fields in CrO/Pd(buffer)/[Co/Pd]exchange bias systems. The magnitude of the exchange bias field is, over a wide temperature range, virtually unaffected by the Pd thickness variation between 1 and 2 nm.
虽然由于反铁磁和磁电CrO(0001)上钯（Pd）覆盖层的边界极化，诱导其自旋极化是可能的，但在单畴状态下，Pd薄膜本身似乎是铁磁性的，这可能是应变的结果。在导带中，我们发现了在CrO(0001)单晶上的Pd薄膜中存在铁磁自旋极化的实验证据，特别是在薄膜极限情况下，Pd厚度约为1 - 4纳米。实际上，在310 K时，即高于块状CrO的奈尔温度时，在CrO(0001)上10 Å厚的Pd薄膜中存在显著的自旋极化。虽然CrO(0001)的表面矩倾向于沿表面法线排列，但对于CrO上的Pd，自旋极化包含一个面内分量。CrO(0001)上Pd吸附层中的应变似乎与自旋极化逆光电子能谱中测量的自旋极化相关。通过测量CrO/Pd（缓冲层）/[Co/Pd]交换偏置系统中的交换偏置场，提供了CrO上Pd磁化的进一步证据。在很宽的温度范围内，交换偏置场的大小实际上不受1到2纳米之间Pd厚度变化的影响。
