Heat transport of the quasi-one-dimensional alternating spin chain material (CH3)2NH2CuCl

Abstract

We report a study of the low-temperature heat transport in the quasi-one-dimensional S = 1/2 alternating antiferromagnetic-ferromagnetic chain compound (CH 3 ) 2 NH 2 CuCl 3 . Both the temperature and magnetic-field dependencies of thermal conductivity are very complicated, pointing to the important role of spin excitations. It is found that magnetic excitations act mainly as the phonon scatterers in a broad temperature region from 0.3 to 30 K. In magnetic fields, the thermal conductivity shows drastic changes, particularly at the field-induced transitions from the low-field Néel state to the spin-gapped state, the field-induced magnetic ordered state, and the spin polarized state. In high fields, the phonon conductivity is significantly enhanced because of the weakening of spin fluctuations.

Thermal conductivity of the diamond-chain compound Cu3(CO3)2(OH)2

“…Using x-ray Laue photographs, the large pieces of crystals were cut into thin-plate or long-bar shaped samples with specific orientations. The thermal conductivity was measured at low temperatures down to 0.3 K and in magnetic fields up to 14 T by using a conventional steadystate technique [20,22,24,38]. In these measurements, the magnetic field is either parallel to or perpendicular to the heat current (J H ), which is along the length of the sample ( ∥ J b H ).…”

“…Furthermore, in zero field the temperature dependence of κ is very complicated. A peculiar feature of the ( ) κ T is a three-peak structure at about 2, 8 and 100 K. The positions of these peaks are rather different from that of phonon peak in insulators, which usually locates at 10-20 K. Considering the small values of κ, these peaks are actually caused by the presence of two valley-like minimums at 3 and 17 K. In general, the possible reasons of these minimums in ( ) κ T curves of the magnetic materials could be either the strong phonon scattering by critical spin fluctuations at some magnetic phase transitions or the phonon resonant scattering by some magnetic impurities or lattice defects [15,22,23,28,34,[48][49][50][51][52][53][54]. It has been known that Cu 3 (CO 3 ) 2 (OH) 2 does not exhibit any magnetic phase transition at 3 and 17 K, as the magnetic susceptibility and specific heat data indicate.…”

“…Low-temperature heat transport has recently been found to be an effective way to probe the magnetic excitations and the field-induced quantum phase transitions [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. In particular, a large spin thermal conductivity in spin-chain and spin-ladder systems has been theoretically predicted and experimentally confirmed in such compounds as SrCuO 2 , Sr 2 CuO 3 , CaCu 2 O 3 , Sr 14 Cu 24 O 41 , etc [28][29][30][31][32][33].…”

“…Most of these materials have simple spin structure and strong exchange coupling, which are necessary for producing high-velocity and long-range-correlated spin excitations, while the low dimensionality strongly enhances the quantum fluctuations and ensures a large population of spin excitations. Some low-dimensional magnets however exhibit strong coupling between crystal lattice and spins, which can strongly suppress the phonon heat transport [15,22,34,35]. In this regard, the ultrasonic, thermal expansion and neutron scattering experiments have revealed rather strong magnetoelastic couplings in Cu 3 (CO 3 ) 2 (OH) 2 [11,36,37].…”

Anomalous Thermal Conductivity and Magnetic Torque Response in the Honeycomb Magnet α−RuCl3

“…The Kitaev model [1] has attracted particular attention, both theoretically and experimentally, because it possesses an exactly solvable quantum spin-liquid (QSL) ground state and has possible realizations in a number of candidate materials [2][3][4][5]. Thermal transport measurements have proven to be a powerful tool for elucidating the itinerant nature of QSLs [6,7], as a result of their high sensitivity to the low-energy excitation spectrum, and in fact studies of low-dimensional insulating quantum magnets have revealed very significant contributions to heat conduction from unconventional spin excitations [8][9][10][11][12][13][14][15][16][17][18].…”