49 research outputs found

    Ό\muSR and Neutron Diffraction Investigations on Reentrant Ferromagnetic Superconductor Eu(Fe{0.86}Ir{0.14})2As2

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    Results of muon spin relaxation (ÎŒ\muSR) and neutron powder diffraction measurements on a reentrant superconductor Eu(Fe0.86_{0.86}Ir0.14_{0.14})2_2As2_2 are presented. Eu(Fe0.86_{0.86}Ir0.14_{0.14})2_2As2_2 exhibits superconductivity at Tc on≈22.5T_{\rm c\,on} \approx 22.5~K competing with long range ordered Eu+2^{+2} moments below ≈18\approx 18 K. A reentrant behavior (manifested by nonzero resistivity in the temperature range 10--17.5 K) results from an exquisite competition between the superconductivity and magnetic order. The zero field ÎŒ\muSR data confirm the long range magnetic ordering below TEu=18.7(2)T_{\rm Eu} = 18.7(2) K. The transition temperature is found to increase with increasing magnetic field in longitudinal field ÎŒ\muSR which along with the neutron diffraction results, suggests the transition to be ferromagnetic. The neutron diffraction data reveal a clear presence of magnetic Bragg peaks below TEuT_{\rm Eu} which could be indexed with propagation vector k = (0, 0, 0), confirming a long range magnetic ordering in agreement with ÎŒ\muSR data. Our analysis of the magnetic structure reveals an ordered magnetic moment of 6.29(5) ΌB6.29(5)\,\mu_{\rm B} (at 1.8 K) on the Eu atoms and they form a ferromagnetic structure with moments aligned along the cc-axis. No change in the magnetic structure is observed in the reentrant or superconducting phases and the magnetic structure remains same for 1.8 K ≀T≀TEu\leq T \leq T_{\rm Eu}. No clear evidence of structural transition or Fe moment ordering was found.Comment: 9 pages, 7 figures, to appear in Phys. Rev.

    Tetramer Orbital-Ordering induced Lattice-Chirality in Ferrimagnetic, Polar MnTi2O4

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    Using density-functional theory calculations and experimental investigations on structural, magnetic and dielectric properties, we have elucidated a unique tetragonal ground state for MnTi2O4, a Ti^{3+} (3d^1)-ion containing spinel-oxide. With lowering of temperature around 164 K, cubic MnTi2O4 undergoes a structural transition into a polar P4_1 tetragonal structure and at further lower temperatures, around 45 K, the system undergoes a paramagnetic to ferrimagnetic transition. Magnetic superexchange interactions involving Mn and Ti spins and minimization of strain energy associated with co-operative Jahn-Teller distortions plays a critical role in stabilization of the unique tetramer-orbital ordered ground state which further gives rise to lattice chirality through subtle Ti-Ti bond-length modulations
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