Ho-doped sample simultaneously exhibits high-coercivity and enhanced remnant magnetization with a polar R3c symmetry at room temperature. The onset of R3c to Pnma phase transition is observed at high temperatures in the Ho-doped samples.

In transition metal oxides, quantum confinement arising from a large surface to volume ratio often gives rise to novel physico-chemical properties at nanoscale. Their size dependent properties have potential applications in diverse areas, including therapeutics, imaging, electronic devices, communication systems, sensors, and catalysis. We have analyzed structural, magnetic, dielectric, and thermal properties of weakly ferromagnetic SmFeO 3 nanoparticles of sizes about 55 nm and 500 nm.The nano-size particles exhibit several distinct features that are neither observed in their larger-size variants nor reported previously for the single crystals. In particular, for the 55 nm particle, we observe six-fold enhancement of compensation temperature, an unusual rise in susceptibility in the temperature range 550 to 630 K due to spin pinning, and coupled antiferromagnetic-ferroelectric transition, directly observed in the dielectric constant. I.

No abstract

We study the effect of non-magnetic Zn 2+ (spin-0) and magnetic Ni 2+ (spin-1) impurities on the ground state and low-lying excitations of the quasi-one-dimensional spin-1/2 Heisenberg antiferromagnet Sr2CuO3 using inelastic neutron scattering, specific heat and bulk magnetization measurements. We show that 1 % Ni 2+ doping in Sr2CuO3 results in a sizable spin gap in the spinon excitations, analogous to the case of Ni doped SrCuO2 previously reported [ref. 1]. However, a similar level of Zn 2+ doping in SrCuO2, investigated here for comparison, did not reveal any signs of a spin gap. Magnetic ordering temperature was found to be suppressed in the presence of both Zn 2+ and Ni 2+ impurities, however, the rate of suppression due to Ni 2+ was found to be much more pronounced than for Zn 2+ . Effect of magnetic field on the ordering temperature is investigated. We found that with increasing magnetic field, not only the magnetic ordering temperature gradually increases but the size of specific heat anomaly associated with the magnetic ordering also progressively enhances, which can be qualitatively understood as due to the field induced suppression of quantum fluctuations.

No abstract