Abstract
Effect of energetic C60 cluster ion irradiation on magnetic properties in FeRh thin films was examined by SQUID and XMCD measurements. The XMCD signal for the C60 irradiated samples is larger than that for the C1 samples in the initial stage of the irradiation. In contrast, as for the irradiation with larger ion fluence, the XMCD spectrum for the sample irradiated with C1 ion is larger than that for the sample irradiated with C60 cluster ion. Although the magnetization for the C60 irradiation samples continuously decreases with increasing in the ion fluence, the saturation magnetization for the C1 irradiation samples increases with increasing in the ion fluence. Considering these different behaviors in the irradiation induced ferromagnetism, the cluster ion can effectively deposit the apparent elastic collision energy at the surface region in the film, which effectively causes the ferromagnetic state at the surface of the films.
Highlights
Iron rhodium is known to exhibit a first order phase transition from anti-ferromagnetic (AF) to ferromagnetic (FM) near room temperature
It has been revealed that the density of energy deposited through elastic collisions between ion species and sample species should be one of the crucial factors in determining ion irradiation induced magnetization of FeRh samples, which means that such ferromagnetic ordering can be ascribed to the lattice defects introduced in the B2 crystal structure due to the ion irradiation.[7]
The crystal structure of the unirradiated samples was confirmed to be composed of single phase of B2 FeRh by θ-2θ X-ray diffraction (XRD) using 30 keV CuKα radiation
Summary
Iron rhodium is known to exhibit a first order phase transition from anti-ferromagnetic (AF) to ferromagnetic (FM) near room temperature. Much attention has been focused on B2 (CsCl)type FeRh thin films due to their possible application to novel spin devices, such as thermal assist type magnetic recording system.[1,2] In our previous studies on this material, we have ever revealed that energetic ion beam irradiation induces FM state below room temperature where it exhibits intrinsically AF states without any structural phase transition.[3,4,5,6] In addition, we have revealed that the excess ion irradiation causes the structural change from FM B2-type to non-magnetic A1 (random fcc)-type crystal structure that is a high temperature phase in the equilibrium phase diagram.[6] It has been revealed that the density of energy deposited through elastic collisions between ion species and sample species should be one of the crucial factors in determining ion irradiation induced magnetization of FeRh samples, which means that such ferromagnetic ordering can be ascribed to the lattice defects introduced in the B2 crystal structure due to the ion irradiation.[7]. This pronounced effect is considered to be due to the ion clustering effect, which was first observed in sputtering
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