Bi3+ Doping Induced Suppression of Spin Flop Transition in DyMnO3

Doped perovskite manganites [1] have attracted renewed attention due to scientific interest and prospective novel device applications [2]. Substitution of `Dy
<sup>3+</sup>
' site with isovalent `Bi
³⁺
' in DyMnO
₃
without changing effective `Mn' valence could generate the A-site cationic mismatch to introduce a “chemical pressure”, leading to an enhanced distortion of perovskite structure [3], which has not been explored widely. Our experiments indicate formation ofBi
<sub>2</sub>
O
<sub>3</sub>
impurity when the doping is greater than 2%. In this work, effect of `Bi' doping in Dy
_1-x
Bi
_x
MnO
₃
is studied on the variation of structural and magnetic properties. It is observed that the intensity of (210) plane of orthorhombic structure decreases with `Bi' content and vanishes at x = 0.15 (Fig. 1). In the magnetization data, the ZFC-FC curves become irreversible upon doping with `Bi'. At 2 K, a spin flop like transition is observed in DyMnO
₃
and it gradually decreases with Bi doping with an enhancement of HC and Mr, indicating a change from soft to hard magnet contrary to the case of `Bi' doped LaMnO
<sub>3</sub>
[4]. Specific heat capacity data implies a ferroelectric transition Tlock to vanish upon doping with `Bi'. In addition, the FC magnetization data fitted well with a phenomenological model and the related magneto-caloric effects will be discussed.