QFS2016 Book of Abstracts

Abstracts

P1.39 Quantum Phases of Spin-1 Bosons on the AB Chain Cruz Greis(1), Franco Roberto(2), Silva-Valencia Jereson(2) 1) Universidad Santo Tom´as, Departamento de Ciencias B´asicas, Carrera 9 # 52-11, Bogot´a, Colombia. 2) Universidad Nacional de Colombia, Departamento de F´ısica, Carrera 30 # 45, Bogot´a, Colombia. Motivated by recent studies on optical lattices, we explore the one-dimensional structure of spin-1 bosons in an alternating lattice, assuming on-site Coulomb repulsion and antiferromagnetic interaction. We determine the quantum phases by calculations of ground-state energy via Density Matrix Renormalization Group. Results in the chemical potential in the thermodynamic limit give evidence of insulators in integer and semi-integer densities, and superfluid phases. We show the phase diagram for small quantum fluctuations considering spin-1 bosons as a function of the spin-dependent term, where important contributions of the exchange interaction in the evolution of insulator regions are found. P1.40 Magnetic properties and magnetocaloric effect in MnCo 0 . 95 Cu 0 . 05 Ge compound Gao Tian, Qi Ningning, Sun Chao, Zhou Tao, Liu Yongsheng Shanghai University of Electric Power, Department of Physics, No. 2588 Changyang Road, 200090 Shanghai, China We studied the structure, magnetic and magnetocaloric (MC) properties of MnCo 0 . 95 Cu 0 . 05 Ge alloy. A single phase of the Ni 2 In-type hexagonal structure (space group P63/mmc) is proven to be formed in the final sample by X-ray powder diffraction pattern at room temperature. A second-order paramagnetic-ferromagnetic transition is observed at Curie temperature T C ≈ 256 K, accompanied by a large MC effect. Below T C , the sample shows strong ferromagnetism, which is caused by the sub-lattice Mn-Mn ordering. The maximum value of magnetic entropy change is evaluated to be 13 . 64 J kg − 1 K − 1 for a magnetic field change ∆H = 7 T. The corresponding relative cooling power reaches 869 J kg − 1 .

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