Role of the apical oxygen in the low-temperature magnetoelectric effect inRMnO3(R = Ho and Lu)

Abstract

Infrared active phonons of HoMnO 3 and LuMnO 3 single crystals are studied under an applied magnetic field below Ho 3+ spin ordering at T = 4.2 K. Interestingly, relatively strong mode energy shifts, induced by the magnetic field, are observed in HoMnO 3 but are absent in the nonmagnetic rare-earth compound LuMnO 3 . We associate the large magnetoelectric effects in HoMnO 3 with a mechanism of charge transfer between Ho 3+ and apical oxygen. Also, the exact values of the published polarization change under the applied magnetic field are predicted with no adjustable parameters.

Infrared Active Phonons and Optical Band Gap in Multiferroic GdMnO3Studied by Infrared and UV-Visible Spectroscopy

“…As polycrystalline sample has mixed ab-plane and c axis response, so the BEC have been calculated as an average over different optical response, however, it is believed that effective charges do not depend strongly on orientation [22]. The present Z * values are quite close to those reported for other compounds of RMnO 3 such as DyMnO 3 [12], HoMnO 3 [23], LuMnO 3 [24], and YMnO 3 [25], as shown in Table IV. It is noteworthy that obtained values clearly deviate from their nominal values (Z Gd/Mn = 3 and Z O = −2) but small as compared with other ferroelectric materials such as BaTiO 3 , SrTiO 3 , WO 3 [26,27].…”

Signatures of the Chiral Anomaly in Phonon Dynamics

“…Magnetically induced effective phonon charges are not unique to WSM: they also occur e.g. in multiferroic materials 29 . Indeed, according to group theory, phonons that are IR inactive at B 0 = 0 may become IR active at B 0 = 0, provided that they belong to the direct product of axial and polar irreducible representations (irreps) 30 .…”

Magnetostriction of Hexagonal HoMnO3 and YMnO3 Single Crystals

“…Шайхутдинов P6 3 ; она имеет более низкую магнитную анизотропию [6,7]. Также возможно, что в пространственной группе P63cm только треть из спинов иона Mn 3+ направлены вдоль кристаллографической гексагональной оси, тогда как в фазе P63cm спины Mn 3+ повернуты в плоскости на 90 • [19][20][21].…”