AC Magnetoelectrical Susceptibility Study of Multiferroics
Multiferroics are materials in which ferroelectric and magnetic e.g., ferromagnetic or antiferromagnetic orders co-exist. Some of these show the magnetoelectric effect which is the coupling between electric and magnetic degrees of freedom leading to induction of electric polarization by an applied magnetic field and also induction of magnetic polarization by an applied electric field. Multiferroic substances have attracted attention in recent times as they are expected to show relatively larger magnetoelectric effect than others. TbMnO3 and DyMnO3 are prototypical magnetoelectric multiferroics where ferroelectricity develops due to a magnetic phase transition to a spiral magnetic ordered phase. Cu2OSeO3 is another magneto-electric material and is the only one in which magnetoelectric (ME) susceptibility dM/dE (i.e. the change in magnetization by the application of an AC electric field) measurements have been performed to successfully map the magneto-electric phase diagram. During this work, dM/dE measurements were used to map the phase di- agram of Cu2OSeO3 for directions of applied magnetic and electric fields different from that reported so far. This success in Cu2OSeO3 thus became the motivation to make similar attempts on TbMnO3 and DyMnO3. The samples were first oriented to identify the crystallographic axes, then DC magnetic susceptibility and AC mag- netoelectric susceptibility measurements were carried out. The DC magnetization measurements for TbMnO3 showed clear signatures of phase transitions and thus subsequently dM/dE measurements were performed with an AC applied electric field in order to perform a sensitive probe of the phase diagram. But for TbMnO3, dM/dE response could not be observed in any portion of the phase diagram i.e. at ifferent magnetic field and temperature. This entire procedure from Cu2OSeO3 to he manganates have been presented here in this report.