Dimensional Antiferromagnet Research Articles

Crystallographic Two Sublattice System –Staggered Susceptibility and Induced Staggered Magnetization in Paramagnetic State–

Magnetic basic properties of the crystallographic two sublattice (C 2 ) system in which magnetic ions at these lattice points have inequivalent g -tensors, are rigorously studied on the basis of the linear response theory. Such a C, system under a uniform field is quite equivalent to a fictitious single lattice (C 1 ) system under both a uniform and a staggered fields. So in such a C 2 system, the staggered magnetization as well as the uniform magnetization is induced in the paramagnetic state by applying a uniform field. On these facts, a possibility to derive the staggered susceptibility from the experimentally observed uniform and staggered magnetizations was examined based on the symmetry of zero field Hamiltonian of the system. Application of the result to the existing one and two dimensional Heisenberg antiferromagnets is discussed with some promising examples.

Magnetic Behaviours of a Random Magnet, NipMg(1-p)(OH2)

Magnetic behaviours of the mixed crystal, Ni p Mg (1- p ) (OH) 2 , as a randomly diluted magnet of the quasi-two dimensional antiferromagnet, Ni(OH) 2 , were investigated by measurements of the susceptibility and the magnetization. In pure Ni(OH) 2 , the three kinds of exchange interactions were estimated as follows: J 1 / k ∼2.70 K, J 2 / k ∼-0.28 K and J 3 / k ∼-0.09 K. The anisotropy energy mainly comes form the crystalline anisotropy. In Ni p Mg (1- p ) (OH) 2 the paramagnetic susceptibilities obeyed the Curie-Weiss law well above the critical temperature, T N ( p ), for the concentration, \(0.4{\lesssim}p{\le}1\). Below p ∼0.4, the susceptibilities obeyed the Curie-Weiss law, but with the different Curie and the Weiss constants in the lower and higher temperature regions. This may result from ferromagnetic short range order in the lower temperature region.

NMR relaxation at low temperature in one dimensional antiferromagnets: Comparison between [formula omitted] and [formula omitted

The proton spin-lattice relaxation time T 1 has been measured at low temperatures in spin 5 2 (CH 3) 4NMnCl 3 (TMMC) and spin 1 2 CuCl 22NC 5H 5 (CuPC). The two systems have very different temperature dependences which we attribute to the different spin values.

ON THE MAGNETIC SUSCEPTIBILITIES OF SOME IMINOXYL RADICALS

Abstract Magnetic susceptibilities of organic stable radicals, derivatives of 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl (TANOL), have been measured. The magnetic susceptibility of Ethyl-TANOL showing a broad maximum at a temperature of 0.17 K agrees well with the antiferromagnetic Heisenberg linear chain model, while that of Methyl-TANOL exhibits a characteristic feature of the three dimensional antiferromagnet.

Light scattering from two-magnon modes in K 2NiF 4

Measurements of Raman scattering from two magnon excitations in the two dimensional antiferromagnet K 2NiF 4 are extended to 275°K. The zeroth frequency moment of the magnon signal has a temperature dependence essentially the same as that found in the three dimensional antiferromagnet, NiF 2. No indications of critical behavior are apparent in the first frequency moment for K 2NiF 4 in contrast to the case of three dimensional antiferromagnets.

Linear chain antiferromagnetism in FeOHSO 4

Magnetic susceptibility measurements on Fe OH SO 4 suggest linear chain antiferromagnetism up to at least 200°K with a transition to three dimensional antiferromagnetism at 56°K. Mössbauer spectra show magnetic hyperfine splitting up to ∼ 90°K and this is interpreted in terms of intrachain spin correlation with relaxation effects caused by interchain spin relaxation. The 4·2°K spectrum is strongly asymmetric because of the admixture of nuclear eigenfunctions by non-parallel magnetic and quadrupolar principal axes systems. Using this the first complete derivation of a complete set of hyperfine interaction parameters from a Mössbauer spectrum is made and correlated with the crystallographic structure.

Metal insulator phase transition and magnetic properties of V<inf>n</inf>O<inf>2n-1</inf>

Magnetic properties of V n O 2n-1 system, which shows the temperature induced metal insulator phase transition at T t , were studied by the measurement of magnetic susceptibility and Mossbauer effect. It was observed that V 3 O 5 , V 4 O 7 , V 5 O 9 , V 6 O 11 , V 7 O 13 , and V 8 O 15 order anti-ferromagnetically at 70, 40, 30, 23, 51, and 7 K, respectively. V 3 O 5 behaves like a low dimensional antiferromagnet. V 7 O 13 is a metallic antiferromagnet. Above T t (metallic phase) the total susceptibility χ mol can be represented by χ mol = C obs / T-θ + χ 0 . C obs is in a good agreement with calculated value C cal , assuming that the material is ionic (V+3and V+4in a paramagnetic state). Density of electronic state of Fermi level D_{(\epsilon_{f})_{x}_{0} was calculated from χ 0 assuming Pauli paramagnetism and compared with the D_{(\epsilon_{f})_\gamma obtained by specific heat measurement.

The effect of crystal field anisotropy on the Neel temperature TN of layered Heisenberg antiferromagnets

The variation of Néel temperature of two dimensional antiferromagnets, with a crystal field anisotropy has been studied by the Green function method in the Callen decoupling approximation. A good qualitative agreement with the experimental results of Matsuura et al. has been obtained.

Linear Chain Antiferromagnetism in Copper Benzoate

Various magnetic properties of one dimensional antiferromagnet Cu(C6HsC00)2 ·3H20 were investigated by means of magnetic susceptibility, magnetic torque, NMR, and ESR measurements. The results show that this compound is one of the best one dimensional antiferromagnets known at present. An intrachain exchange interaction J/K was estimated to be -8. 6±1 °K while no second order phase change was found down to 1. 4 °K. ESR line width at room temperature was not explained by an usual treatment and an anisotropic exchange effect was newly taken into account. However, other anomalies of the line width such as the frequency, temperature, and angular dependences appeared at low temperature regions were not yet explained.