Presence of a paramagnetic phase well below the ferromagnetic onset in _x

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: 4 April 2003

Abstract

Partial replacement of by in depresses the ferromagnetic order of the compound and leads to a stepwise magnetic behavior characterized by two subsequent transitions at and . 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 . It coexists with the ferromagnetic phase below and with both the ferromagnetic and antiferromagnetic phases below with a reduced but significant fraction. The magnetization jump at is possibly a conversion of the remaining paramagnetic phase into the ferromagnetic phase.