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Abstracts
P1.16
Magnetization process, thermodynamics and magnetocaloric effect of
the spin-1/2 XXZ Heisenberg cubooctahedron
Karlova Katarina(1), Strecka Jozef(2), Madaras Tomas(3)
P. J. ˇSaf´arik University, Faculty of Science, Institute of Physics, Park Angelinum
9, 040 01 Koˇsice, Slovakia
Magnetic properties of the spin-1/2 XXZ Heisenberg cubooctahedron are
examined using exact numerical diagonalization as a function of the exchange
anisotropy. While the Ising cubooctahedron exhibits in a low-temperature
magnetization curve only one-third magnetization plateau, another four
intermediate plateaux can be found in magnetization curve of the Heisenberg
cubooctahedron for arbitrary but non-zero exchange anisotropy. The novel
plateaux generally extend over a wider range of magnetic fields with the
exchange anisotropy. The Heisenberg cubooctahedron exhibits in a vicinity
of all magnetization jumps anomalous thermodynamic behavior accompanied
with a giant magnetocaloric effect.
P1.17
Magneto-thermodynamic signatures of quantum critical points of the
ferrimagnetic mixed-spin Heisenberg chains
Strecka Jozef(1), Verkholyak Taras(2)
1) Institute of Physics, Faculty of Science, P.J. Safarik University, Park
Angelinum 9, 040 01 Kosice, Slovakia
2) Institute for Condensed Matter Physics, National Academy of Sciences of
Ukraine, 1 Svientsitskii Street, L’viv-11, 79011, Ukraine
Thermodynamic properties of the ferrimagnetic mixed spin-(1/2,S) Heisenberg
chains are examined using quantum Monte Carlo simulations. Zero-temperature
magnetization curves involve two quantum critical points with magnetization
cusps, which determine a breakdown of Lieb-Mattis ferrimagnetism and Luttinger
spin liquid, respectively. Thermodynamic signatures of these quantum critical
points are examined at finite temperatures. While the magnetization curve at
non-zero temperatures is almost without any signature, other thermodynamic
response functions (susceptibility, specific heat, entropy) provide a more clear
evidence of quantum critical points through local maxima or minima, respectively.
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