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Title: Ti substitution for Mn in MnCoGe - the magnetism of Mn0.9Ti0.1CoGe
Authors: Wang, JL
Shamba, P
Hutchison, WD
Din, MFM
Debnath, JC
Avdeev, M
Zeng, R
Kennedy, SJ
Campbell, SJ
Dou, SX
Keywords: Neutrons
Issue Date: 15-Nov-2013
Publisher: Elsevier Science
Citation: Wang, J. L., Shamba, P., Hutchison, W. D., Md Din, M. F., Debnath, J. C., Avdeev, M., Zeng, R., Kennedy, S. J., Campbell, S. J., & Dou, S. X.(2013). Ti substitution for Mn in MnCoGe - the magnetism of Mn0.9Ti0.1CoGe. Journal of Alloys and Compounds, 577, 475-479. doi:10.1016/j.jallcom.2013.06.134
Abstract: Bulk magnetization measurements (5–320 K; 0–8 T) reveal that below room temperature Mn0.9Ti0.1CoGe exhibits two magnetic phase transitions at ∼178 K and ∼280 K. Neutron diffraction measurements (3–350 K) confirm that the transition at ∼178 K is due to the structural change from the low-temperature orthorhombic TiNiSi-type structure (space group Pnma) to the higher temperature hexagonal Ni2In-type structure (space group P63/mmc), while the transition at ∼280 K originates from the transition from ferromagnetism to paramagnetism. The magnetocaloric behaviour of Mn0.9Ti0.1CoGe around Tstr ∼ 178 K and TC ∼ 280 K as determined via the magnetic field and temperature dependences of DC magnetisation are given by the maximum values of the magnetic entropy changes −Δ S M max = 6.6 J kg−1 K−1 around Tstr ∼ 178 K, and −Δ S M max = 4.2 J kg−1 K−1 around TC ∼ 280 K for a magnetic field change of ΔB = 0–8 T. Both structural entropy – due to the unit cell expansion of ∼4.04% – and magnetic entropy – due to an increase in the magnetic moment of ∼31% – are found to contribute significantly to the total entropy change around Tstr. Critical analysis of the transition around TC ∼ 280 K leads to exponents similar to values derived from a mean field theory, consistent with long-range ferromagnetic interactions. It was found that the field dependence of −Δ S M max can be expressed as −Δ S M max ∝ Bn with n = 1 for the structural transition around Tstr and n = 2/3 for the ferromagnetic transition around TC, thereby confirming the second order nature of this latter transition.© 2013, Elsevier Ltd.
Gov't Doc #: 5072
ISSN: 0925-8388
Appears in Collections:Journal Articles

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