Europhys. Lett.
Volume 62, Number 5, June 2003
Page(s) 732 - 738
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 May 2003
DOI: 10.1209/epl/i2003-00434-8
Europhys. Lett., 62 (5) , pp. 732-738 (2003)

Presence of a paramagnetic phase well below the ferromagnetic onset in $\chem{La}$ 0.67-x $\chem{Bi}$ x $\chem{Ca_{0.33}MnO_{3}}$

J. R. Sun1, B. G. Shen1, J. Gao2, Y. Fei3 and Y. P. Nie4

1  State Key Laboratory for Magnetism, Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences - Beijing 10080, PRC
2  Department of Physics, the Hong Kong University - Pokfulam Road, Hong Kong, PRC
3  Australian Nuclear Science and Technology Organization, Lucas Heights, Laboratories Menai 2234, Australia
4  Department of Physics, Sichuan University - Chengdu 19904, PRC

(Received 21 January 2003; accepted in final form 4 April 2003)

Partial replacement of $\chem{La}$ by $\chem{Bi}$ in $\chem{La_{0.67}Ca_{0.33}MnO_{3}}$ depresses the ferromagnetic order of the compound and leads to a stepwise magnetic behavior characterized by two subsequent transitions at $\sim 120$ $\un{K}$ and $\sim
225$ $\un{K}$. Based on a combined study of the electron spin resonance spectra and the thermal and isothermal magnetization, a complete scenario for the phase separation that causes the complex behavior has been given. It is found that the paramagnetic phase exists in a wide temperature region even below the ferromagnetic onset at $\sim
225$ $\un{K}$. It coexists with the ferromagnetic phase below $\sim 240$ $\un{K}$ and with both the ferromagnetic and antiferromagnetic phases below $\sim 190$ $\un{K}$ with a reduced but significant fraction. The magnetization jump at $\sim 120$ $\un{K}$ is possibly a conversion of the remaining paramagnetic phase into the ferromagnetic phase.

75.50.Dd - Nonmetallic ferromagnetic materials.
76.30.-v - Electron paramagnetic resonance and relaxation.
75.30.Vn - Colossal magnetoresistance.

© EDP Sciences 2003