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arXiv · 1310.8370

Orbital magnetic moment and coercivity of SiO$_{2}$-coated FePt nanoparticles studied by x-ray magnetic circular dichroism

Y. Takahashi·T. Kadono·V. R. Singh·V. K. Verma·K. Ishigami·G. Shibata·T. Harano·A. Fujimori·Y. Takeda·T. Okane·Y. Saitoh·H. Yamagami·S. Yamamoto·M. Takano
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Abstract

We have investigated the spin and orbital magnetic moments of Fe in FePt nanoparticles in the $L$1$_{0}$-ordered phase coated with SiO$_{2}$ by x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements at the Fe $L_{\rm 2,3}$ absorption edges. Using XMCD sum rules, we evaluated the ratio of the orbital magnetic moment ($M_{\rm orb}$) to the spin magnetic moment ($M_{\rm spin}$) of Fe to be $M_{\rm orb}/M_{\rm spin}$ = 0.08. This $M_{\rm orb}/M_{\rm spin}$ value is comparable to the value (0.09) obtained for FePt nanoparticles prepared by gas phase condensation, and is larger than the values ($\sim$0.05) obtained for FePt thin films, indicating a high degree of $L$1$_{0}$ order. The hysteretic behavior of the FePt component of the magnetization was measured by XMCD. The magnetic coercivity ($H_{\rm c}$) was found to be as large as 1.8 T at room temperature, $\sim$3 times larger than the thin film value and $\sim$50 times larger than that of the gas phase condensed nanoparticles. The hysteresis curve is well explained by the Stoner-Wohlfarth model for non-interacting single-domain nanoparticles with the $H_{\rm c}$ distributed from 1 T to 5 T.

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Y. Takahashi, T. Kadono, V. R. Singh, V. K. Verma, K. Ishigami, G. Shibata, T. Harano, A. Fujimori, Y. Takeda, T. Okane, Y. Saitoh, H. Yamagami, S. Yamamoto, M. Takano. 2013-10-31. Orbital magnetic moment and coercivity of SiO$_{2}$-coated FePt nanoparticles studied by x-ray magnetic circular dichroism. https://doi.org/10.1103/physrevb.90.024423

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