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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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