Field effects on spontaneous magnetization reversal of bulk BiFe_0.5Mn_0.5O₃, an effective strategy for the study of magnetic disordered systems

Abstract

We report a comprehensive study of the spontaneous magnetization reversal (MRV) performed on the disordered polycrystalline perovskite BiFe(0.5)Mn(0.5)O(3), an intriguing compound synthesized in high pressure-high temperature conditions. In disordered systems, the origin of MRV is not completely clarified, yet. In BiFe(0.5)Mn(0.5)O(3), compositional disorder involves the ions on the B-site of the perovskite determining the presence of mesoscopic clusters, characterized by high concentrations of iron or manganese and thus by different resultant magnetization. This leads to the observation of two singular fields H(1) and H(2) dependent on the degree of inhomogeneity, unpredictably changing from sample to sample due to synthesis effects. These fields separate different magnetic responses of the system; for applied fields H < H(1), the Fe and Mn clusters weakly interact in a competitive way, giving rise to MRV, while for an intermediate field regime the energy of this weak interaction becomes comparable to the energy of the system under field application. As a consequence, the zero field cooled magnetization thermal evolution depends on the sample degree of inhomogeneity. In this field regime, applied field Mössbauer spectroscopy indicates that the iron rich clusters are highly polarized by the field, while the largest part of the material, consisting of AFM clusters characterized by axial anisotropy and uncompensated moments, shows soft or hard magnetism depending on T. Above the higher singular field, the M(T) curves show the trend expected for a classical antiferromagnetic material and the competitive character is suppressed. The MRV phenomenon results to be highly sensitive on both the thermal and magnetic measurement conditions; for this reason the present work proposes a characterization strategy that in principle has a large applicability in the study of disordered perovskites showing similar phenomenology.

Effects of different high‐pressure syntheses on the magnetization reversal properties of Bi2FeMnO6 ceramics

“…The adjacent Mn-O and Fe-O sublattices distorting leads to the canting angle of Fe-O-Mn. It has been reported [21,22,24,37] that the spin canting would originate from the D-M interaction, which is directly coupled to the tilting of the adjacent Fe-O and Mn-O octahedral. And it can account for the occurrence of the FM phase in some multiferroic perovskites.…”

“…Bi 2 FeMnO 6 ceramics synthesized at high pressure are the former series of materials. [21,36,37] It is possible to switch the two magnetized states by varying the magnetic field without relaxation and attenuation. This unusual magnetization reversal behavior allows such materials to be used in the preparation of magnetic memory or magnetic switching devices.…”

“…[17,18] For the Bi 2 (M′ 2(1−x) M″ 2x )O 6 materials, there have also been some reports about the magnetization reversal properties. [19][20][21][22][23][24] In 2009, [19] the magnetization reversal properties were observed in Bi 2 FeCrO 6 and La 2 FeCrO 6 samples that were synthesized at high pressure by Vijayanandhini et al The compensation temperatures with the applied magnetic field of .1 T are 164 K (Bi 2 FeCrO 6 ) and 109 K (La 2 FeCrO 6 ). Then the magnetization reversal effects were also observed in La 1.9 Bi .1 FeCrO 6 , [20] Bi 2 (Fe 2−2x Mn 2x )O 6 ceramics.…”

“…Then the magnetization reversal effects were also observed in La 1.9 Bi .1 FeCrO 6 , [ 20 ] Bi 2 (Fe 2−2 x Mn 2 x )O 6 ceramics. [ 21–24 ]…”

Temperature-Induced Reversible and Irreversible Transitions between Metastable Perovskite Phases in the BiFe1−yScyO3 Solid Solutions

“…In cases when the required pressure is abovẽ 8 GPa, the obtained amounts are hardly enough, even for the crystal structure characterization. The cases when researchers managed to measure dielectric properties of the high-pressure synthesized ceramics are rather rare [3][4][5][6][7].…”