aDepartment of Physics, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China bSchool of Physics Science and Technology, Yangtze University, Jingzhou 434020, People's Republic of China Received 16 July 2006; accepted 3 September 2006. Available online 20 September 2006.
The special formula of La2/3+ySr1/3−yMn1−yCryO3 with [Mn3+]/([Mn4+] + [Cr3+]) ratio fixed at optimal proportion 2:1 was designed to tune colossal magnetoresistance (CMR) response around room temperature and test the possibility of ferromagnetic (FM) interaction of hetero-ionic coupling between Mn3+ and Cr3+. The polycrystalline bulk samples were fabricated by the traditional solid-state reaction method. The structural, magnetic, electrical transports and magnetoresistance (MR) properties were investigated. An enhancement of CMR at room temperature with appropriate content y has been observed, meanwhile, substituting Cr for Mn in manganites shows inefficiency in lowering ferromagnetic–paramagnetic (FM–PM) transition temperature Tc and metal–insulator (M–I) transition temperature Tp. Experimental results indicate that there might exist a FM coupling between Mn3+ and Cr3+.