Magnetic anisotropy in detwinned Tb_0.9Dy_0.1BaCo₂O_5.5single crystal

Abstract

Magnetic properties of detwinned Tb0.9Dy0.1BaCo2O5.5 single crystals have been studied. The admixture of Dy, introduced only for technological reasons, has no essential influence on the behaviour of the rare earth subsystem of this compound, which is determined by the electronic structure of the Tb3+ ions. It is shown that the Co3+ ions are Ising ions, with the easy axis along the a axis, in the temperature range 2–276 K (TC). The Tb3+ ions in the AFM phase (T<TN 2 = 3.4 K) are strongly anisotropic, with easy axes [101] and . The magnetic field induced phase transitions have been studied, and it is shown that they are determined by anisotropic Co3+–Tb3+ exchange interactions. It is shown that the Co3+ subsystem is ferrimagnetically ordered within the range TN< T<TC (TN = 250 K, TC = 275.5 K) and that the ferrimagnet–antiferromagnet phase transition is of first order, whereas the ferrimagnet–paramagnet phase transition is of second order. In the region of antiferromagnetic ordering of the Co3+ ions, metamagnetic phase transitions have been observed for . In the temperature range 2 K<T< 170 K, a small ferromagnetic component along the a axis has been observed. This could indicate partial lack of compensation of the antiferromagnetic order. The magnetic susceptibility in the vicinity of the metal–insulator transition (340 K) has been measured. It is found that this transition is accompanied by a structural phase transition responsible for the essential changes of the magnetic anisotropy of Co ions.

X-ray and neutron diffraction studies of coupled structural phase transitions in DyBaCo2O5.5

“…To resolve the issue, we have made an assumption [6] that the low-temperature magnetic transition in the Tb material coincides with a structural one that double c axis: c 4 = 2c 3 . Unlike the Tb material, reflection (1, 1, 1) is absent in the case of the DyBaCo 2 O 5.5 below 200 K. However, the other reflection (0, 0, 1) with l -odd still coexists with (1,1,2), and the magnetic transition at In the range of this wide temperature hysteresis, the unusual magnetic properties of field-cooled and zero-field-cooled crystals in the temperature range 120 < T < 210 K [12,13], probably, may be due to coexistence of two phases with different crystal and magnetic structures.…”

“…3(c) is similar to that of the superstructure pair (3, 0, 1) + (0, 3, 1). In the range of this wide temperature hysteresis, the unusual magnetic properties of field-cooled and zero-field-cooled crystals in the temperature range 120 < T < 210 K [12,13], probably, may be due to coexistence of two phases with different crystal and magnetic structures.…”

Large single crystals of LnBaCo2O5.5: Initial nucleation, growth and study

“…It has been refined on the basis of 147 magnetic reflections measured at T ¼ 248 K. The basic functions of irreducible representations for the Pmma space group with k ¼ 0 wave vector of magnetic structure are given [19] by f ¼ 1 ffiffi [7,20], and we compare with the experimental magnetic Bragg intensities only the models that include either f x or a x of the same irreducible representation for both pyramidal and octahedral sublattices to provide the second-order Hamiltonian invariance to the symmetry transformations. Four models presented in Table 3 and in Fig.…”

Switching from unusual to usual ferromagnetism in “112” LnBaCo2O5.50±δ: By calcium doping

“…Sufficient efforts are given to explore their fascinating magnetic, electrical and magnetotransport properties [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. It exhibits a rich phase diagram since the electronic states of Co and surrounding oxygen are changed by varying d [6,12].…”