Magnetothermal properties of the Heisenberg-Ising orthogonal-dimer chain with triangular X X Z clusters

Article

关键词: HELIX-COIL TRANSITION;    EXACT GROUND-STATE;    MAGNETIZATION PLATEAUS;    SAWTOOTH CHAIN;    SPIN CHAINS;    QUANTUM;    MODEL;    BEHAVIOR;    SYSTEM;    PHASE;   

DOI  :  10.1103/PhysRevB.86.054412

来源: SCIE

【 摘 要 】

We study a spin-1/2 model with triangular X X Z clusters on the orthogonal-dimer chain in the presence of an external magnetic field. First, we discuss the case where the triangular clusters are coupled via intermediate classical Ising spins. Diagonalization of the triangular X X Z clusters yields the exact ground states; finite-temperature properties are computed exactly by an additional transfer-matrix step. A detailed analysis reveals a large variety of ground states at magnetization M equal to fractions 0, 1/4, and 1/2 of the saturation magnetization M = 1. Some of these ground states break translational symmetry spontaneously and give rise to doubling of the unit cell. In a second part, we present complementary numerical data for the spin-1/2 Heisenberg model on the orthogonal-dimer chain. We analyze several examples of T = 0 magnetization curves, entropy as a function of temperature T and magnetic field, and the associated magnetic cooling rate. Comparison of the two models shows that in certain situations the simplified exactly solvable model yields a qualitatively or sometimes even quantitatively accurate description of the more challenging quantum model, including a case which may be relevant to experimental observations of an enhanced magnetocaloric effect in the two-dimensional compound SrCu2(BO3)(2).

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