PdNi和PdFe铁磁合金自旋记忆长度的测量
Measurement of spin memory lengths in PdNi and PdFe ferromagnetic alloys
摘要：
弱铁磁合金被几个研究小组用于超导/铁磁混合系统的研究。由于在这种合金中的自旋翻转和自旋轨道散射破坏了对相关性到铁磁材料中的渗透，因此希望直接测量这种合金中的自旋记忆长度。利用电流垂直面巨磁电阻方法测量了4.2K下溅射Pd_（0.88）Ni_（0.12）和Pd_（0.987）Fe_（0.013）合金的自旋记忆长度。合金被纳入到各种类型的混合自旋阀，和自旋记忆长度确定的Valet-Fert自旋输运方程的磁阻与合金厚度的数据拟合。对于PdNi合金的情况，自旋记忆长度的结果值为lsf（PdNi）= 2.8 +/-0.5nm和5.4 +/-0.6nm，这取决于PdNi是否被相邻的坡莫合金层交换偏置。对于PdFe，自旋记忆长度稍长，lsf（PdFe）= 9.6 +/-2 nm，与早期测量结果一致，表明该材料中的自旋轨道散射较低。不幸的是，即使是较长的自旋记忆长度在PdFe可能不够长，以便于观察自旋三重态超导相关性预测发生在超导/铁磁混合系统中存在的磁性不均匀性。
英文摘要：
Weakly ferromagnetic alloys are being used by several groups in the study of superconducting/ferromagnetic hybrid systems. Because spin-flip and spin-orbit scattering in such alloys disrupt the penetration of pair correlations into the ferromagnetic material, it is desirable to have a direct measurement of the spin memory length in such alloys. We have measured the spin memory length at 4.2 K in sputtered Pd0.88Ni0.12 and Pd0.987Fe0.013 alloys using methods based on current-perpendicular-to-plane giant magnetoresistance. The alloys are incorporated into hybrid spin valves of various types, and the spin memory length is determined by fits of the Valet-Fert spin-transport equations to data of magnetoresistance vs. alloy thickness. For the case of PdNi alloy, the resulting values of the spin memory length are lsf(PdNi) = 2.8 +/- 0.5 nm and 5.4 +/- 0.6 nm, depending on whether or not the PdNi is exchange biased by an adjacent Permalloy layer. For PdFe, the spin memory length is somewhat longer, lsf(PdFe) = 9.6 +/- 2 nm, consistent with earlier measurements indicating lower spin-orbit scattering in that material. Unfortunately, even the longer spin memory length in PdFe may not be long enough to facilitate observation of spin-triplet superconducting correlations predicted to occur in superconducting/ferromagnetic hybrid systems in the presence of magnetic inhomogeneity.
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