Showing papers on "Spin canting published in 1995"

Antiferromagnetic Ordering and Spin Structure in the Organic Conductor, κ -(BEDT-TTF ) 2 Cu[N(CN ) 2 ]Cl

Abstract: The magnetism of an insulator, $\ensuremath{\kappa}$-(BEDT-TTF${)}_{2}$Cu[N(CN${)}_{2}$]Cl, situated near the 10 K superconducting phase in $\ensuremath{\kappa}$-type BEDT-TTF family, has been studied by ${}^{1}$H NMR for the first time. A commensurate antiferromagnetic ordering with a moment of (0.4--1.0) ${\ensuremath{\mu}}_{B}$/dimer was found below 26--27 K. The features, quite different from the conventional spin density wave, suggest that the magnetic order is driven by strong electron correlation rather than by nesting of the Fermi surface, and that the present salt is a Mott insulator. Magnetization measurements show spin canting parallel to the conducting layer below 23 K at low fields.

Magnetic properties of feroxyhyte (δ-FeOOH)

Abstract: Magnetization curves and high-field Mossbauer spectra are used to deduce a model for the magnetic order in synthetic samples of δ-FeOOH (feroxyhyte), which takes account of the changes in magnetization when the samples are heated at 105 °C. Feroxyhyte is essentially a planar antiferromagnet with the net sublattice moments aligned parallel or antiparallel to c. Each particle acquires a net moment due to the very small number of layers along the c-direction, and the presence of surface steps causing the formation of ferrimagnetic domains with an odd number of layers. There is some spin canting which is related to the crystallinity of the sample. The decrease in magnetization following heating is mainly due to an increase in the extent of antiferromagnetic coupling between the closely packed ferrimagnetic particles, but changes in the spin canting within the bulk may also contribute. A typical, rather well crystallized specimen has magnetization σ=14 JT−1 kg−1 and Curie temperature Tc=455 K.

Magnetic properties of (Sr, Ba)2Cu3O4Cl2: Two-dimensional antiferromagnetic cuprates containing two types of Cu-site

Abstract: Magnetization and neutron-diffraction measurements have been performed on single crystals of Ba 2 Cu 3 O 4 Cl 2 and Sr 2 Cu 3 O 4 Cl 2 , isomorphous layered insulating cuprates containing two types of Cu-site in the Cu 3 O 4 planes. Neutron-diffraction measurements revealed both three-dimensional antiferromagnetic order of Cu 2+ spins on one of the sites (A-site), which are connected by the Cu(A) O Cu(A) 180°-bonds, and successive order of the other site (B-site), which locates at the centre of the Cu(A)O 2 square. Magnetization measurements indicate an in-plane weak ferromagnetic moment below the Neel temperature T N due to spin canting within the Cu 3 O 4 planes.

Structural and magnetic phase transitions in bis-(alkyl ammonium) manganese tetrachlorides (CnH2n+1NH3)2MnCl4 withIn = 5, 7, and 9

Abstract: The structural and magnetic phase transitions in the series of compounds (CnH2n + 1 NH3)2MnCl4 with n = 5,7, and 9 are studied by means of X-ray diffraction, differential scanning calorimetry, and magnetic susceptibility experiments. Like the previously studied first members of the series (n = 1 to 3), these perovskite-like layer compounds undergo at low temperature an antiferromagnetic transition with weak ferromagnetic moment due to spin canting. In the paramagnetic domain, the magnetic susceptibility is sensitive to a first-order phase transition which could be due to the freezing of alkyl ammonium groups. Les transitions magnetiques et structurales dans la serie de composes (CnH2n + 1 NH3)2MnCl4 avec n = 5, 7, et 9 sont etudiees par diffraction des rayons X, calorimetrie et mesures de susceptibilite magnetique. Comme les premiers membres de la serie precedemment etudies (n = 1 a 3), ces composes lamellaires de type perovskite presentent, a basse temperature, une transition antiferromagnetique avec un ferromagnetisme faible resultant d'un “spin-canting”. Dans le domaine paramagnetique, la susceptibilite est sensible a une transition structurale du premier ordre qui est vraisemblablement due au gel des groupements alkyl-ammonium.

Magnetism and cation distribution in iron zinc silicates

Abstract: Silicates in the Fe2−xZnxSiO4 system are known to give a limited solution series [1] with the olivine structure on the iron side (end-member fayalite) and phenakite structure on the zinc side (end-member willemite). To obtain information about the magnetic structure and cation distribution, synthetic powder samples in this series (x = 0.2, x = 1.4) have been investigated by neutron diffraction. The fayalite sample (x = 0.2) gives magnetic diffraction patterns below the Neel temperature (∼ 56 K). On the M1 site spin canting (with respect to the b-axis) of 41° and 16° and magnetic moments of 4.2μB and 2.4μB are found at 2 K and 40 K, respectively. The spin canting on the M2 site, supposed from Mossbauer measurements [2] could not be confirmed. The magnetic moment is 4.0μB and 3.6μB at 2 K and 40 K, respectively. Zinc clearly prefers the M1 lattice site. In the willemite sample (x = 1.4), a small superimposed intensity at 2 K could indicate the magnetic order as expected, based on magnetically split Mossbauer spectra [2] . Zinc prefers the Znl site.