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

• Published in: Journal of applied physics 2017-02, Vol.121 (8)
• Main Authors: Sarkar, Tanushree, Manna, Kaustuv, Elizabeth, Suja, Anil Kumar, P. S.
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Applied physics; Chemical synthesis; Coercivity; Coupling; Crystal structure; Entropy; Ferroelectric materials; Ferroelectricity; Heat exchange; Hysteresis loops; Organic chemistry; Raman spectra; Rare earth elements; Room temperature; Symmetry
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4977103

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 P63 cm 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 P63 cm 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.