Neutron diffraction measurements, performed in presence of an externalmagnetic field, have been used to show structural evidence for the kineticarrest of the first-order phase transition from (i) the high temperatureaustenite phase to the low temperature martensite phase in the magnetic shapememory alloy Ni37Co11Mn42.5Sn9.5, (ii) the higher temperature ferromagneticphase to the lower temperature antiferromagnetic phase in the half-doped chargeordered compound La0.5Ca0.5MnO3 and (iii) the formation of a glass-likearrested state (GLAS). The CHUF (cooling and heating under unequal fields)protocol has been used to establish phase coexistence of metastable andequilibrium states of GLAS and also to demonstrate the devitrification of thearrested metastable states in the neutron diffraction patterns. We also explorethe field-temperature (H,T) phase diagram for the two compounds, which depictsthe kinetic arrest line TK(H). TK is seen to increase as H increases.
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