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Singlecrystal ac susceptibility measurements on [Co(NH3)6][CuCl5], a 3D, S=1/2 Heisenberg antiferromagnet Single crystal magnetization and susceptibility studies on CuCl2DMSO, a salt with quasi 1d ferromagnetic interactionsWe report the results of magnetic susceptibility investigations of single crystals ofCuCI 2 ·2DMSO and of a polycrystalline sample of CuBr 2 ·2DMSO, [DMSO = (CH3bSO] two isostructural, orthorhombic linear chain S = 1/2 compounds. The principal susceptibilities of the chloride all show rounded maxima near 11 K, then gradually decrease at different rates at lower temperatures. There is no indication of long range ordering above 2 K. All three susceptibilities show evidence of uniaxial anisotropy contributions within the exchange Hamiltonian with the b axis corresponding to the magnetic easy axis. The data are interpreted in terms of the results of Bucher and Honerkamp with an antiferromagnetic exchange constant of -8.2 K and 10% Isinglike anisotropy. The susceptibility of the bromide can be described as a Heisenberg antiferromagnetic chain with J Ik = -11.0(2) K above 40 K but at lower temperatures the susceptibility rises as if7% of the moments were paramagnetic. Since this behavior is observed in different batches, it may have its origin in spin canting.

Copper chloride monoTMSO has previously been shown to be an example of a spin-1/2 linear chain with Heisenberg ferromagnetic exchange (J/k≊39 K). Motivated by the proportionality between the temperature derivative of the linear magnetic birefringence (TDLMB) and the magnetic specific heat, we have determined the birefringence of the title compound along the 010 and 100 faces between 3.1 and 260 K. The data along the 010 face show no evidence of magnetic behavior. They could be fit to a Debye function with a θD of 123 K. Along the 100 face, a sharp spike was seen at 3.42 K, indicating the transition to long-range magnetic order. The data for the 100 face could not be fit to a Debye function alone but were successfully modeled as a sum of a lattice contribution (θD ≊244 K) and a ferromagnetic contribution with an exchange constant J/k between 30 and 60 K. The data was insensitive to the magnitude of J.

The design and operating characteristics of a helium cryostat for a vibrating sample magnetometer are described. The cryostat incorporates an exchange gas enclosure for the sample and a carbon-glass resistance thermometer. The design permits a reduced background signal, increased temperature stability, and longer operating times than previous commercially available cryostats.

Articles you may be interested inPerturbative approximation scheme for isolated impurity bonds in the twodimensional spin1/2 Heisenberg antiferromagnet J. Appl. Phys. 75, 5532 (1994); 10.1063/1.355679 Raman spectra of twodimensional spin1/2 Heisenberg antiferromagnets J. Appl. Phys. 75, 6340 (1994); 10.1063/1.355393 Isolated ferromagnetic bonds in the twodimensional spin1/2 Heisenberg antiferromagnet (abstract) The compounds CuX 2 '2DMSO (X = CI,Br; DMSO = [(CH3)2S0J) are being studied as model compounds for the S = ! Heisenberg antiferromagnetic linear chain system (HB AF).This report presents the results of birefringence measurements on both the bromide (CDB) and the chloride (CDC) between 3.5 and 250 K. The temperature derivative of the birefringence has been compared to the theoretical predictions for the magnetic specific heat of the model. Both protonated and deuterated versions were studied but no significant differences were observed. Both the (001) and (010) faces ofCDB were studied; the results were different but both sets of data correspond to the specific heat of the HB AF with an exchange constant of Jar = -11.4 ± 0.3 K. The exchange strength found for CDC was lel = -8.1 ± 0.3 K.These values are consistent with those found from magnetic measurements. It was necessary to account for nonmagnetic contributions to the birefringence. The presence of small amounts of exchange anisotropy could not be detected in the data. 3548