High field induced spin reorientations in Ho _0.24 Y _2.76 Fe ₅ O ₁₂

Abstract

Some precise magnetization measurements have been performed on Ho 0.24 Y 2.76 Fe 5 O 12 single crystals under static magnetic fields up to 16 Tesla and in the temperature range (2-30 K). As previously observed in pulsed magnetic fields, the change from the spontaneous ferrimagnetic structure in zero magnetic field to the fully ferromagnetic one in high field, takes place through several intermediate phases separated by step-like magnetization jumps. Whole H-T phase diagrams have been determined for the three main cubic axes and also when the sample can rotate freely. We show that the Ising model, commonly used to account for the large magnetocristalline local anisotropy of the Ho 3+ moments, is in worst agreement with our static measurement than with the previous pulsed fields experiments and then a more realistic model is needed and will be discussed.

High field magnetic transitions in the mixed holmium–yttrium iron garnet Ho0.43Y2.57Fe5O12

“…The chemical composition was checked using a scanning microscope (JSM-840A), electronic microprobe and chemical analysis and also by checking carefully the specific magnetization of each sample in the low field range. The results of these different methods show a greater dispersion than for the previously studied compound (x = 0.24 ± 0.01) [8] and the composition was found to vary from x = 0.41 to 0.45. So we take x = 0.43 ± 0.02, and all the magnetization results are reported in Bohr magnetons per Ho 0.43 Y 2.57 Fe 5 O 12 formula unit.…”

“…Previous experiments on related compounds in pulsed fields [4][5][6][7] or in static fields [8] have shown that, at sufficiently low temperature, the increase of the applied field H gives rise to 'orientational' phase transitions with step-like magnetization curves, corresponding to the passage from the initial ferrimagnetic state to the ferromagnetic saturated state through several canted phases. The number of these transitions depends on the orientation of the external field with respect to the crystallographic axes.…”

High-field orientational magnetic phase diagrams of the mixed holmium–yttrium iron garnet Ho0.43Y2.57Fe5O12

“…At T = 0 K, the three Ho moments are equal, implying that during these discontinuous transitions M Ho jumps from one type of 111 direction to another, with simultaneous and appropriate change in M Fe orientation. This model has been useful for a qualitative description of the different orientational phases and the transitions involved between them in such diluted rare-earth compounds, but it does not account quantitatively for all the observations [4,5,10,11]. In particular, when the temperature is raised the observed magnetic transitions become smoother and smoother and vanish all together more quickly at a critical temperature T * (=18.9 K, present work).…”

“…Here n is the isotropic molecular-field coefficient. We deduced earlier [10] that its value can be taken equal to 2.2 T mol/μ B (i.e. H mol = 11 T).…”

“…Numerous studies have been dedicated to the high-field magnetic transitions in the ferrimagnetic mixed holmiumyttrium iron garnet Ho x Y 3−x Fe 5 O 12 (x < 0.8) compounds [1][2][3][4][5][6][7][8][9][10][11]. Most of them were carried out under high pulsed magnetic fields [1][2][3][4][5][6][7][8][9].…”