Structure And Characteristics Of Hexagonal RMn_1-xFe_xO₃?R=Sc,Lu? Multiferroic Ceramics

In recent years,multiferroic materials have been a hotspot in the fields of both condensed matter physics and materials research because of their rich physical significance and huge application potential.As an important member of the single multiferroic materials,hexagonal manganite?RMnO₃?has attracted increasing scientific interests.The focuses of research are to increase the Néel temperature,reduce the leakage conductivity,and obtain the room-temperature magnetoelectirc coupling.Fe³⁺-sbutitution is an effective way to increase the Néel temperature in the hexagonal maganite.In the present work,the preparation,structural evolution,and multiferroic property variation of Fe³⁺ion-modified hexagonal manganite ceramics are systematically studied.And room-temperature magnetoelectric coupling is observed in both ScMn_1-xFe_xO₃ and LuMn_0.5Fe_0.5O₃,which may be caused by the coupling between the ferroelectric ordering and short-range spin ordering.This is a new way to obtain room temperature magnetoelectric coupling effect.The following main conclusions were obtained:The ScMn_1-xFe_xO₃ ceramics were prepared by a standard solid-state reaction process.In the compositions range of 0?x?0.2,the compound stabilizes in hexagonal phase at room temperature,with P6₃cm space group.The remanent ferroelectric hysteresis loop measurement?RHM?confirmed the room-temperature ferroelectricity,while the local spontaneous polarization values were calculated to be 4.53,4.57,and4.50?C/cm²,respectively.The Fe³⁺-substitution can greatly enhance the magnetic properties in ScMn_1-xFe_xO₃ ceramics.By inducing the Fe³⁺ions,the magnetic exchange has been enhanced and the geometric frustration has been suppressed.Therefore,the antiferromagnetic transition temperature T_N increased from 130 K via135 K to 140 K,and the spin reorientation temperature T_SR increased from 58 K to 80K and 100 K.Additionally,the Fe³⁺-substitution enhanced the short-range magnetic ordering in ceramic materials,which could be attributed to the existence of magnetism in the ceramics above T_N.The dielectric anomalies near T_N has been observed,indicating the strong spin lattice coupling in the ceramics.The room temperature magnetoelectric coefficient was quite stable with increasing magnetic field around 0.8 mV/cm·Oe in ScMn_0.8Fe_0.2O₃ ceramics,which was probably caused by the coupling of ferroelectric ordering with the short-range spin ordering.LuMn_0.5Fe_0.5O₃ ceramics were prepared by a standard solid-state reaction process,and the effect of Fe³⁺-substitution on magnetic properties and magnetoelectric coupling were investigated.The magnetic susceptibility vs.temperature curves suggest the antiferromagnetic transition with the T_N¹03 K and a spin re-orientation transition at T_SR⁵7 K.Comparing with the parent phase LuMnO₃,the magnetic properties were enhanced in the LuMn_0.5Fe_0.5O₃ ceramics,which could be attributed to the enhanced magnetic exchange and the suppressed geometric frustration by Fe³⁺ions substitution.Dielectric anomalies were observed at T_N and T_SR,indicating the existence of magnetodielectric coupling induced by the strong spin lattice coupling.In addition,the magnetic properties measurement confirmed the existence of the short-range spin ordering in the LuMn_0.5Fe_0.5O₃ ceramics below 325K.The room temperature magnetoelectric coefficient was quite stable with increasing magnetic field with value around 0.075mV/cm·Oe.The characteristics of magnetoelectric coupling coefficient of LuMn_0.5Fe_0.5O₃ ceramics were similar to those of ScMn_0.8Fe_0.2O₃ ceramics,which should be the result of the coupling of the ferroelectric ordering and the short-range spin ordering.This phenomenon was rarely reported in other hexagonal manganites and their solid solutions,which could be a new way to realize room temperature magnetoelectric coupling.