Experimental Study of the Magnetocaloric Effect in the Two-Dimensional Quantum System Cu(tn)Cl2

L. Baranováa, R. Tarasenkob, A. Orendáčováb, M. Orendáčb, V. Pavlíkc, A. Feherb aInstitute of Construction, Technology and Management, Department of Applied Mathematics, Civil Engineering Faculty, Technical University of Košice, Vysokoškolská 4, 042 00 Košice, Slovakia bInstitute of Physics, Faculty of Science, P.J. Šafárik University, Park Angelinum 9, 041 54 Košice, Slovakia cInstitute of Experimental Physics of SAS, Watsonova 47, 040 01 Košice, Slovakia

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Magnetocaloric studies of a two-dimensional antiferromagnet Cu(tn)Cl2 (tn=1,3-diaminopropane=C3H10N2) have been performed by adiabatic magnetization and demagnetization measurements, in the temperature range from 0.2 to 4 K and magnetic fields up to 2 T. The compound represents an S=1/2 spatially anisotropic triangular-lattice antiferromagnet. The magnetocaloric measurements were focused at the identification of the phase transition to the magnetically ordered state which was not indicated in the previous specific heat studies. Furthermore, the interplay of the magnetic-field induced easy-plane anisotropy and the intrinsic spin anisotropy present in the studied system should manifest in low magnetic fields. The obtained results of the magnetocaloric experiments of Cu(tn)Cl2 indicate a double crossover from the normal to inverse magnetocaloric effect (MCE). The first crossover from the normal to inverse MCE occurring at about 0.3 K can be attributed to the competition of the aforementioned anisotropies. The second crossover from the inverse to normal MCE observed at about 2.2 K might be ascribed to the formation of spin vortices stabilized by the easy-plane anisotropy introduced by magnetic field.

DOI: 10.12693/APhysPolA.126.256 PACS numbers: 75.50.Ee, 75.30.Sg