Spintronics, involving the generation, manipulation and detection of the spin polarized electrons, has been rapidly advancing since its emergence. Compared with the traditional magnetic-field-based control, spin transfer torque through spin polarized current, and pure spin current has been considered to be the most promising technique to manipulate the moment of the nanomagnets. The Pt films in contact with the insulating ferromagnetic layers show ferromagneticlike transport properties, as pointed out by C.L. Chien’s group in the Johns Hopkins University recently. It becomes crucial important to ascertain the magnetic proximity effect in the Pt films adjacent to an insulating ferromagnet.
As is known, Pt as well as Pd nearly fulfills the Stoner’s criterion, and both of them can be spin polarized when they are in contact with metallic ferromagnets, which are the classical representatives showing magnetic proximity effect. However, there is no direct information on the magnetization of Pt adjacent to insulating ferromagnets.
Prof. CAI Jianwang and Lu yuming, one of his graduate students at Institute of Physics, Chinese Academy of Sciences, collaborated with Dr. Y.Choi at Argonne National Laboratory, and Prof. C.L.Chien’s group in The Johns Hopkins University and others in USA, have recently reported the quantitative results of Pt moment at low and room temperatures in YIG/Pt films by x-ray magnetic circular dichroism measurement. This observation indicates strong proximity effects and induced magnetic ordering in Pt on magnetic insulators and their contribution to the spin-related measurements should not be neglected. In addition, they have found that ferromagneticlike transport properties that are absent in GGG/Pt samples are also different from common uniform magnetic material. Furthermore, they conclude that the electronic structure of the Pt layers, reflected by the great change in the ordinary Hall effect coefficient and electric resistivity, is strongly modified by the YIG film underneath. Above results appeared in Physical Review Letters 110, 147207 (2013).
This work is supported by the National Basic Research Program of China, and National Natural Science Foundation of China.

CONTACT:
Prof. CAI Jianwang
Institute of Physics, Chinese Academy of Sciences
Email: jwcai@iphy.ac.cn

Fig. 1. (a) Normalized synchrotron x-ray absorption spectra (XAS), and (b) corresponding x-ray magnetic dichroism (XMCD) with an in-plane magnetic field of ±500 Oe from the YIG/Pt(1.5 nm) at 300 K and 20 K. Inset compares the first derivative of the XAS spectra with the XMCD signal ofL3edge obtained at 20 K. Error bars are included in the XMCD results to indicate measurement noise level.

Fig.2. (a) Longitudinal and transverse MR curves of a YIG/Pt(1.5 nm) sample measured at 300 K and 5 K with electrode configuration shown in the inset; (b) and (c) coupled MR and Nernst effect measurements for a YIG/Pt(4 nm) sample; and (d) Pt thickness dependence of AMR ratio for YIG/Pt at 300 K and 5 K. The solid lines are guides for the eye. Inset in figure (d) plots the resistivity as a function of in-plane field direction (8 kOe) for a representative sample YIG/Pt(1.5 nm) at 300 K, and the solid line is a fitting result using cosine square function.

Fig.3. (a) Temperature dependence of the AMR for a YIG/Pt(1.5 nm) and a YIG/Pt(4 nm) film; (b) Comparison of the thickness dependent Pt thin film resistivity grown on YIG and GGG substrates as a function of temperature; and (c) ordinary Hall coefficient measured for Pt films grown on YIG and GGG substrates.