Evidence of cluster glass phase, exchange bias, reversible magnetocaloric effect and study of electrical properties in Ni1-xCdxCr2O4 (x=0-0.30) spinel

Effect of cadmium (Cd) substitution on magnetic and electrical properties of spinel Ni(1-x)CdxCr(2)O(4) (x = 0-0.30) samples have been studied. Due to non-Jahn-Teller Cd ion substitution, a structural transition from the tetragonal (I4(1)/amd) to cubic (Fd $(3) over bar $m) phase is seen at room temperature. The long-range competitive ferrimagnetic and antiferromagnetic interactions in the x = 0.05 and 0.10 samples are responsible for the observed large value of coercive and exchange bias field. Cd substitu-tion significantly enhances the antiferromagnetic component of canted spin structure of NiCr2O4 and leads to a cluster glass phase for x = 0.30 samples. Observed memory effect and relaxation of isothermal remanent magnetization confirms the metastability and nonequilibrium dynamics in the glassy phase. For x = 0.20 sample, we have observed reversible magneto-caloric behavior with a maximum negative entropy change of -Delta S-M = -1.031(3) x 10(-4)cal/gK . Dielectric, impedance and ac conductivity data have been investigated in the temperature range of T = 27-300 K and frequency range of f = 20-10(5) Hz. Study of impedance spectra and ac conductivity indicates non Debye type of dielectric relaxation and correlated barrier hopping (CBH) of charge carriers is controlling the conduction mechanism in these samples.