Journal of Magnetism and Magnetic Materials 69 (1987) 267-275 North-Holland, Amsterdam 267 zyxwvutsr MAGNETIC AND “Fe MhSSBAUER STUDIES OF COLLINEAR SPIN ROTATION IN Ho,Fe,,B zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Akira FUJITA *, Hideya ONODERA, Hiroshi YAMAUCHI, Motohiko YAMADA, Hisao YAMAMOTO The Research Institute for Iron, Steel and Other Metals, Tohoku University, Sendai 980, Japan Satoshi HIROSAWA and Masato SAGAWA Sumitomo Special Metals Co. Ltd, Egawa, Shimamotocho, Mishima-gun, Osaka 618, Japan Received 18 November 1986; in revised form 24 June 1987 Magnetic properties of HqFe,,B compounds have been studied by the “Fe Mossbauer effect and magnetization measurements. The axes of easy and hard magnetizations he along the [OOl] and the [lOO] directions in the tetragonal structure, respectively, above T,, = 58 K. From the comparison of the Miissbauer results with the magnetization measure- ments, it became clear that the Fe and the Ho moments tilt &linearly from the c-axis to the [110] direction throughout the temperature range of 4.2-58 K, and the canting angle reaches to 22’ at 4.2 K. The Mossbauer spectra are consistently resolved with six subspectra above T,, and with twelve below TX, together with reasonable site-assignments. We have estimated the mean Ho moment at lO.OP,, using the mean Fe moment of 2.3~~ derived from the average hyperfine field or using the magnetization of Y,Fe,,B as the Fe-sublattice magnetization of Ho,Fe,,B. 1. Introduction For these years, much attention has been focused on the magnetic properties of rare earth-iron-boron compounds R,Fe,,B which have a tetragonal crystal structure, because these have a variety of spin structures accompanied by a large magnetocrystalline anisotropy. Some of these compounds have been found to exhibit a spin reorientation transition in the course of tempera- ture change [l-15]. The spin reorientation will attribute to a different temperature dependence of the competing anisotropies between the axial Fe and the planar R-ion or between the second and the fourth order crystal field terms in the ani- sotropy constant K, of the R-ion. So far, the Nd 2Fe,,B compound has been studied most pre- cisely among the R,Fe,,B compounds because of the principal constituent of the permanent magnet * Present address: Kawasaki Steel Corp., Kawasaki-cho, Chiba 260, Japan. with the highest (BH),, [16,17]. Neutron diffrac- tion, magnetization and 57Fe MSssbauer measure- ments have revealed that the Nd,Fe,,B com- pound exhibits spin canting from the [OOl] (c = axis) to the [llO] direction below zyxwvutsrqponmlkjihg Tsc = 148 K. A neutron diffraction study [18] has estimated the magnetic moments of Fe and Nd in Nd,Fe,,B on the conception of non-collinear spin, arrangement, hereon those given for Fe and Nd are somewhat different from other results. A recent Mijssbauer study [19] also has suggested that the direction of the mean Nd moment tilt further away from that of the Fe spins at the low temperatures. The non-collinear spin arrangement between Fe and Nd ions in the canting state seems to be favorable if the 3d-4f exchange interaction is not strong enough to completely overcome the axial ani- sotropy energy of the Fe-sublattice. The magnetic properties similar to those of Nd,Fe,,B may be expected to be observed in Ho,Fe,,B, too, except for the sign of the 3d-4f exchange interaction, because both Nd3+ and Ho3’ ions in the ground 0304-8853/ 87/ $03.50 0 Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)