Investigation of multiferroicity, spin-phonon coupling, and unusual magnetic ordering close to room temperature in LuMn0.5Fe0.5O3

Abstract

We report the detailed experimental characteristics of LuMn0.5Fe0.5O3 synthesized by the wet chemical method and proclaim it as a new member of the multiferroic family. The compound stabilizes in P63cm crystal symmetry. It exhibits a spin re-orientation transition at TSR and an antiferromagnetic transition at TN. In addition, our magnetization vs. temperature data reveals an extra broad maximum close to room temperature; unseen in earlier studies. By invoking the compatible nature of the magnetic exchange path in P63cm symmetry, we have argued that the origin lies in the intraplane short-range spin ordering. Heat capacity is measured and analysed to elucidate the magnetic entropy. Though long-range antiferromagnetic ordering vanishes at TN ∼ 103 K, we find the experimental magnetic entropy calculated till 200 K is less by a significant amount from the value of theoretical spin randomization magnetic entropy; further supporting the existence of spin ordering beyond TN and even above 200 K. While the specific heat data and phonon modes of Raman spectra show a signature of spin-phonon coupling at TSR and TN both, dielectric anomaly indicating a magnetoelectric effect is seen only at TN. Piezoresponse force microscopy and ferroelectric hysteresis loop measurement confirm the room-temperature weak ferroelectricity with a saturation polarization value 0.007 μC/cm2 and low coercive field. Furthermore high-temperature dielectric characteristics reveal the ferroelectric transition at around 900 K and exhibit Maxwell-Wagner type relaxation. The present work serves as a bridge between h-RMnO3 and rare earth ferrite RFeO3. It assumes significance in the light of recent research developments in hexagonal RFeO3 (mainly h-LuFeO3) in the context of room-temperature multiferroicity and magnetoelectricity.

Crystal Structure and Concentration-Driven Phase Transitions in Lu(1−x)ScxFeO3 (0 ≤ x ≤ 1) Prepared by the Sol–Gel Method

“…In addition, new intense bands were visible at 113, 419, 497, and 657 cm −1 . The newly appeared bands were characteristic of the hexagonal phase of LuFeO 3 and similar compounds [ 27 , 45 , 46 , 47 , 48 , 49 ]. For the non-centrosymmetric hexagonal crystal symmetry with the P6 3 cm space group, one can expect to observe 38 Raman-active modes distributed by symmetry in the following manner [ 46 , 47 , 49 ]: …”

Hybridization and Decay of Magnetic Excitations in Two-Dimensional Triangular Lattice Antiferromagnets

“…In this context, one of the key issues is the correlation between spin and lattice degrees of freedom, and thus studying the spinlattice coupling is important for uncovering the underlying microscopic mechanisms in these intriguing multiferroic materials. As such, the experimental evidence of the spin-lattice coupling has been previously observed in a series of experiments: X-ray and neutron diffraction, [133][134][135][136][137] Raman and infrared optical spectroscopy, [138][139][140][141][142][143][144][145][146] thermal conductivity, 147,148 elastic moduli, 77,78 and thermal expansion 7,149 measurements.…”

Room‐temperature multiferroic characteristics and unique vortex domain structures of h‐Yb1−xInxFeO3 solid solutions

“…41 Besides, the short-range magnetic ordering structure can also contribute to the remnant magnetization. 38 It remains as a future issue to determine the dominant mechanism.…”

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