R. Mahendiran

Polycrystalline insulating ferromagnetic double perovskite La2CoMnO6 possessing a monoclinic structure and a high Curie temperature (TC = 222 K) was rapidly synthesized (∼30 min) by irradiating a stoichiometric mixture of oxides with microwaves. The sample exhibits negative magnetostriction (λpar), i.e., contraction of length along the magnetic field direction in the ferromagnetic state. At 10 K, λpar does not show saturation up to a magnetic field of 50 kOe, where it reaches 610 × 10−6, which is one of the highest values of magnetostriction found so far among perovskite oxides with 3d ions. The magnitude of λpar decreases monotonically as the temperature increases and becomes negligible above TC. The giant magnetostriction in this double perovskite is suggested to originate from large spin–orbit coupling associated with Co2+ (d7) cation. The obtained magnetostriction value is comparable to λpar = 630 × 10−6 in an identical composition obtained through solid-state reaction over several days in a conventional furnace, which indicates the advantages of microwave-assisted synthesis in saving reaction time and electric power without deteriorating physical properties.