High-Pressure Synthesis and Correlation between Structure, Magnetic, and Dielectric Properties in LiNbO₃-Type MnMO₃ (M = Ti, Sn)

Abstract

LiNbO(3)-type MnMO(3) (M = Ti, Sn) were synthesized under high pressure and temperature; their structures and magnetic, dielectric, and thermal properties were investigated; and their relationships were discussed. Optical second harmonic generation and synchrotron powder X-ray diffraction measurements revealed that both of the compounds possess a polar LiNbO(3)-type structure at room temperature. Weak ferromagnetism due to canted antiferromagnetic interaction was observed at 25 and 50 K for MnTiO(3) and MnSnO(3), respectively. Anomalies in the dielectric permittivity were observed at the weak ferromagnetic transition temperature for both the compounds, indicating the correlation between magnetic and dielectric properties. These results indicate that LiNbO(3)-type compounds with magnetic cations are new candidates for multiferroic materials.

Electronic, magnetic and dielectric properties of multiferroic MnTiO3

“…16 The prediction is thereafter validated by the synthesis of the high-pressure form of LN-type FeTiO 3 which is ferroelectric at and below room temperature and weakly ferromagnetic below 120 K. 17 Lately, Inaguma et al 18 synthesized LN-type MnTiO 3 with space group R3c under high pressure and temperature. They investigated its properties and confirmed that this compound is also ferroelectric polar at room temperature and has weak ferromagnetism at 25 K. Recently, Shin et al 19 experimentally demonstrated a high ferroelectric polarization level of ;47 lC/cm 2 in the heteroepitaxial thin film of LN-type ZnSnO 3 following its synthesis using high-pressure method.…”

Weak ferromagnetism and domain effects in multiferroic LiNbO3-type MnTiO3-II

“…The polar lattice distortion was recently predicted to induce weak ferromagnetism in spin-ordered LiNbO 3 -type ATiO 3 (A = Fe, Mn, and Ni) phases through the antisymmetric Dzyaloshinsky-Moriya (DM) exchange interaction, leading to a proposed mechanism for the electric field control of magnetization. 8 Coexistence of weak ferromagnetism and ferroelectricity in LiNbO 3 -type FeTiO 3 and magnetodielectric coupling in MnTiO 3 -II have subsequently been reported, 9,10 but the magnetic structures were not determined. We report here a neutron and magnetization study of the low temperature spin order in MnTiO 3 -II in zero and applied magnetic fields, leading to the discovery of an unusual low field domain reorientation which breaks the powder-averaging diffraction and allows an unambiguous determination of the spin directions.…”

Ambient-temperature high-pressure-induced ferroelectric phase transition in CaMnTi2O6

“…Different from CaMnTi 2 O 6 , in polar ZnTiO 3 [22] or MnTiO 3 [24] the ν 2 [A 1 (2)] Raman mode vanishes in the first-order phase transition, while in CaMnTi 2 O 6 it stays and hardens as an indication of a less abrupt phase transformation. In fact, the behavior observed in CaMnTi 2 O 6 was previously reported in other pressure-induced second-order phase transitions [25] and indicates that even though the mode softening up to the phase transition is not driving the phase transition, it is sensitive to the motion of the ions involved in the transition process.…”

“…The largest coexisting ferroelectric and magnetic effects are found in type-I multiferroics, in which an ambient-temperature ferroelectric compound containing a magnetic ion shows an antiferromagnetic order at sufficiently low temperature. Unfortunately, while most type-I multiferroics have a large spontaneous polarization, they do not show bulk ferroelectricity due to their large leakage and coercive field [2]. Recently, Aimi et al [3] have discovered that CaMnTi 2 O 6 is a multiferroic with a moderate spontaneous polarization of ∼24 μC/cm 2 and the first example of an oxide containing Mn 2+ allowing a polarization reversal at ambient temperature, thus leading to a novel class of type-I multiferroics.…”

“…However, in contrast to CaFeTi 2 O 6 , the square-planar Mn 2+ and the octahedrally coordinated Ti 4+ are shifted along the c axis in CaMnTi 2 O 6 . This breaks the center of inversion, lowering the symmetry from space group P 4 2 Aimi et al [3] have shown that with increasing temperature the off-centering of the square-planar coordinated Mn 2+ and of the Ti 4+ decreases. Concomitantly, the second-harmonicgeneration (SHG) signal decreases monotonically with temperature up to the Curie temperature T c = 630 K, where it becomes zero due to the ferroelectric (space group P 4 2 mc) to paraelectric (space group P 4 2 /nmc) phase transition.…”