Neutron diffraction evidence for kinetic arrest of first order magneto-structural phase transitions in some functional magnetic materials

• Published in: Journal of physics. Condensed matter Vol. 25; no. 49; p. 496011
• Main Authors: Siruguri, V, Babu, P D, Kaushik, S D, Biswas, Aniruddha, Sarkar, S K, Krishnan, Madangopal, Chaddah, P
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 11.12.2013; Institute of Physics
• Subjects: Charge; Condensed matter; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Constants; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Heating; Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.); Magnetic properties and materials; Magnetically ordered materials: other intrinsic properties; Magnetization; Martensitic transformations; Materials science; Neutron diffraction; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Phase transformations; Physics; Transformations; Integrated intensity; Nickel alloys; Magnetization; Phase transformations; Neutron diffraction; Charge ordering; Martensitic transformations; Magnetic field effects; Ferromagnetic-antiferromagnetic transitions; Magnetically soft alloy; Heat treatments; Tin alloys; Shape memory alloy; Manganese alloys; Kinetics; Cobalt alloys; Transition element alloys
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/25/49/496011

Neutron diffraction measurements, performed in the presence of an external magnetic field, have been used to show structural evidence for the kinetic arrest of the first order phase transition from (i) the high temperature austenite phase to the low temperature martensite phase in the magnetic shape memory alloy Ni37Co11Mn42.5Sn9.5, (ii) the higher temperature ferromagnetic phase to the lower temperature antiferromagnetic phase in the half-doped charge ordered compound La0.5Ca0.5MnO3 and (iii) the formation of glass-like arrested states in both compounds. The cooling and heating under unequal fields protocol has been used to establish phase coexistence of metastable and equilibrium states, and also to demonstrate the devitrification of the arrested metastable states in the neutron diffraction patterns. We also explore the field-temperature dependent kinetic arrest line TK(H), through the transformation of the arrested phase to the equilibrium phase. This transformation has been observed isothermally in reducing H, as also on warming in constant H. TK is seen to increase as H increases in both cases, consistent with the low-T equilibrium phase having lower magnetization.