期刊
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
卷 321, 期 2, 页码 61-73出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jmmm.2008.07.029
关键词
Cr alloy; Magnetization; Electrical resistivity; Magnetoresistivity; Specific heat; Thermal expansion
资金
- National Research Foundation of South Africa [SPF200501210005, 2053766, 2072956]
- National Natural Science Foundation of China [10174070]
The magnetic behaviour of a Cr80-xFe20Mnx alloy system with x = 2, 7, 10, 13 and 22 has been investigated in the temperature range 2-400 K through measurements of magnetization, electrical resistivity, magnetoresistivity, specific heat and thermal expansion. The temperature vs. Mn concentration magnetic phase diagram of the system is rich in magnetic behaviour with ferromagnetic (FM), antiferromagnetic (AFM) and paramagnetic phase regions and a spin-glass (SG) region at the lowest temperatures. Phase transition temperatures amongst these different magnetic phases could be identified from well-defined anomalies of magnetic origin that are displayed by graphs of the above-mentioned physical properties as a function of temperature. The time relaxation of the thermo-remanent, isothermal remanent and field-cooled magnetizations below and above the SG freezing temperature show unusual aspects. These relaxations do not follow the usual superposition principle that is expected for typical SG materials. Negative giant magetoresistance (GMR) is observed in the alloys at 4 K. The GMR initially increases sharply on increasing the Mn content in the alloy system, followed by a tendency towards a saturation negative value for concentrations of more than about 10 at% Mn. Low-temperature plots of C-p/T vs. T-2, where C-p is the specific heat, present anomalous behaviour for alloys with x = 2, 10 and 22. For x = 2 the plot shows an upturn at the lowest temperatures that changes over to a prominent downturn for x 10 and 22. This behaviour is attributed to Fe concentration fluctuations in the alloys, confirming the theoretical model of Matthews. (C) 2008 Elsevier B.V. All rights reserved.
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