The Magnetovolume Effect of an Amorphous Magnet Gd_<67>Ni_<33> (Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties)

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We have observed a large magnetovolume effect in a melt spun Gd-rich amorphous magnet Gd_<67>Ni_<33>. The magnet shows the forced volume magnetostriction of a positive value of 3.76 × 10^<-5>T^<-1> at 4.4K, which is almost as same as that of a typical Invar alloy Fe_<65>Ni_<35>, and the spontaneous volume magnetostriction of 1.97 x 10^<-3> at 6.9 K. Both volume magnetostrictions are proportional to the square of temperature. They are explained in the framework of spin fluctuation theory for weak itinerant electron magnets. The effect supports that the Ni constituent has a magnetic moment in the amorphous phase with such a low Ni concentration unlike crystalline Gd-Ni compounds. We propose a simple relation of estimating the magnetic moment which causes the magnetovolume effect. It gives the Ni moment of 0.61 μ_B per atom at 0 K and the magnetovolume coupling constant of 1.20 × 10^<-14>A^<-2>m^2. We also discuss the arrangement of the magnetic moment in the ground state.
社団法人日本物理学会の論文
2003-05-15