title: Disordered ferromagnetism in Ho2NiMnO6double perovskite.
abstract: Magnetic and dielectric properties of the double perovskite Ho2NiMnO6are reported. The compound is synthesized by nitrate route and is found to crystallize in monoclinic P21/n space group. Lattice parameters obtained by refining powder x-ray diffraction data are; a  =  5.218(2) Å, b  =  5.543(2) Å, c  =  7.480(3) Å and the monoclinic angle is [Formula: see text](4). A phase transition is observed at [Formula: see text] K in the temperature-dependent magnetization curve, M(T). The inverse magnetic susceptibility, (1/[Formula: see text]) fits reasonably well with modified Curie-Weiss law by incorporating the paramagnetic response of Ho3+. 1/[Formula: see text] manifests as an upward deviation from ideal Curie-Weiss behaviour well above the ferromagnetic transition. Signs of inherent Griffiths phase pertaining to the Ni/Mn subsystem are visible when one subtracts the Ho3+paramagnetic contribution from total susceptibility and does the power-law analysis. The magnetic hysteresis at 2 K gives the maximum value of magnetization [Formula: see text] [Formula: see text]/f.u. at 50 kOe. Field-derivative of magnetization at 2 K shows discontinuities which indicates the existence of metamagnetic transitions in this compound. This needs to be probed further. Out of the two dielectric relaxations observed, the one at low temperature may be attributed to phononic frequencies and that at higher temperature may be due to Maxwell-Wagner relaxation. A correlation between magnetic and lattice degrees of freedom is plausible since the anomaly in dielectric constant coincides with TC.
authors.affiliation: Department of Physics, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Tirthankar
authors.initials: T
authors.lastname: Chakraborty
authors.forename: Harikrishnan S
authors.initials: HS
authors.lastname: Nair
authors.forename: Hariharan
authors.initials: H
authors.lastname: Nhalil
authors.forename: K
authors.initials: K
authors.lastname: Ramesh Kumar
authors.forename: André M
authors.initials: AM
authors.lastname: Strydom
authors.forename: Suja
authors.initials: S
authors.lastname: Elizabeth