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The magnetic compensation and magnetostriction properties in Fe-doped CoCr2O4 samples have been investigated. Structural and magnetic measurements imply that the doped Fe3+ ions initially occupy the B1 (Cr) sites when x < 0.1, and then mainly take the A (Co) sites. This behaviour results in a role conversion of magnetic contributors and a composition compensation between two competitively magnetic sublattices at x = 0.1. Temperature-dependent compensation has also been found in the samples with x = 0.1-0.22, with the compensation temperature in the range of 40-104 K. The Fe3+ doping also modulates the exchange interaction of the system and prevents the formation of long-range conical order of spins. The magnetoelectric transition temperature at 23 K in CoCr2O4 is shifted to lower temperature by increasing the dopants. The magnetostriction effect in this system has been observed for the first time. The strain has a maximum value of about 280 ppm at x = 0.4. The magnetostriction is consistent with the behaviour of the two magnetic compensations. [ABSTRACT FROM AUTHOR]

Abstract: A series of Co ferrites (Co x Fe3−x O4 (x=0−1)) were prepared using solid-state method in this work. The aging effect of their structures and constrictions of hysteresis loops under low magnetic field were investigated. It was found that during the aging process, the migration of trivalent (bivalent) ions between tetrahedral (A-site) and octahedral (B-site) coordination induced a shrinking of the lattice, which would expand again due to the precipitation of Fe3+ after a much longer aging time. The first process caused a pronounced constriction of the loops, due to the uniaxial anisotropy led by this migration. The depression of constriction could attribute to both the expansion of lattice and the change of ionic ratios as a result of the second-phase-precipitation. The impacts of Co content, aging time and temperature upon the constriction were also discussed. [Copyright &y& Elsevier]