Volume 84, Number 2, October 2008
Article Number 27004
Number of page(s) 4
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 02 October 2008
EPL, 84 (2008) 27004
DOI: 10.1209/0295-5075/84/27004

Unconventional critical behavior in the weak ferromagnet BaIrO3

T. Kida1, A. Senda1, S. Yoshii1, M. Hagiwara1, T. Takeuchi2, T. Nakano3, 4 and I. Terasaki3, 4

1   KYOKUGEN, Osaka University - 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
2   Low Temperature Center, Osaka University - 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
3   Department of Applied Physics, Waseda University - 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan
4   CREST, Japan Science and Technology Agency - Kawaguchi, Saitama 332-0012, Japan

received 7 May 2008; accepted in final form 4 September 2008; published October 2008
published online 2 October 2008

We report the results of ac/dc magnetization study of the critical behavior in a weak ferromagnet BaIrO3. The critical temperature has been determined to be $T_{{\rm c}}$ = 182.8 K by the ac susceptibility measurement. We have analyzed our dc magnetization data near $T_{{\rm c}}$ with the help of the modified Arrott plot method. The critical exponents have been determined to be $\beta $ = 0.82$\pm$0.03, $\gamma$ = 1.03$\pm$0.03, and $\delta$ = 2.20$\pm$0.01, which roughly obeys $\delta =\gamma /\beta +1$. Using these values of $T_{{\rm c}}$, $\beta $, and $\gamma$, we find that each magnetization-field-temperature (M-H-T) behavior below and above $T_{{\rm c}}$ obeys a scaling relation, following a single equation of state in which $M/\vert\varepsilon \vert^{\beta}$ is uniquely related to $H/\vert\varepsilon \vert^{(\gamma +\beta )}$ where $\varepsilon \equiv (T-T_{{\rm c}})/T_{{\rm c}}$. These findings demonstrate that the ferromagnetic transition in BaIrO3 belongs to a new universality class of the second-order phase transition.

75.40 Cx - Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.).
75.60.Ej - Magnetization curves, hysteresis, Barkhausen and related effects.
71.30.+h - Metal-insulator transitions and other electronic transitions.

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