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Interacting magnetic cluster‐spin glasses and strain glasses in Ni–Mn based Heusler structured intermetallics
Author(s) -
Entel Peter,
Gruner Markus E.,
Comtesse Denis,
Sokolovskiy Vladimir V.,
Buchelnikov Vasiliy D.
Publication year - 2014
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201451059
Subject(s) - materials science , condensed matter physics , magnetic refrigeration , spin glass , ferromagnetism , superparamagnetism , antiferromagnetism , austenite , paramagnetism , curie temperature , martensite , magnetic shape memory alloy , tetragonal crystal system , magnetization , phase (matter) , metallurgy , magnetic domain , magnetic field , microstructure , chemistry , physics , quantum mechanics , organic chemistry
Magnetic Ni–Mn based Heusler intermetallics show complex magnetic behavior in connection with martensitic transformations (see, for instance, the phase diagram of Ni–Co–Mn–Sn on the right‐hand side). The cubic austenitic phase at high temperature shows long‐range ferromagnetic order which can considerably be weakened by the appearance of competing antiferromagnetic interactions which are induced by Mn excess and chemical disorder. With decreasing temperature a martensitic/magnetostructural transformation takes place from cubic to non‐modulated/modulated tetragonal/monoclinic or orthorhombic structure, where long‐range ferromagnetic order can no longer be maintained, leading to superparamagnetic behavior. At still lower temperatures superparamagnetism changes to superspin glass because of strong competition of ferromagnetic and antiferromagnetic interactions and chemical disorder. In addition, disorder and local structural distortions can lead to strain glass in austenite, as observed for some non‐magnetic martensitic systems. The magnetic intermetallics are of technological importance in view of their functional properties involving magnetic shape‐memory and exchange‐bias effects as well as magnetocaloric effects. The ‘ferroic cooling’ is of particular relevance since it avoids the use of ozone‐depleting and greenhouse chemicals compared with conventional fluid‐compression technology. Experimental phase diagram of Ni 50 − xCo xMn 39Sn 11 for 0 ≤ x ≤ 10 . Here, T C is the Curie temperature of austenite; at T M the system transforms to paramagnetic martensite and at T S to superparamagnetic martensite (SPM) and then to superspin‐glass martensite (SSG) at T P . The possible strain‐glass phases (labeled by question marks) are predicted because of kinetic arrest phenomena and local distortions associated with the magnetostructural transition and ergodicity breaking by field‐cooling/zero‐field‐cooling experiments.