The static magnetic properties of the easy plane antiferromagnet CsMnBr, were studied by meansof a three-coordinate vibratingsamplemagnetometer in fields up to75 kOe and in the temperature range 1.7-80 K. it was revealed that in some field interval, H 1 e, a magnetization component rMllc appears in the crystal. The results obtained indicate that spins deviate from the basal plane. The phase diarram corcespondin~ to this deviation is discussed.. Recently, a considerable number of theoretical and experimental studies have been devoted to the magnetic properties of the quasi-one-dimensional hexagonal antiferromagnet CsMnBr, (space group D& with lattice parameters a = 7.61 8, and c = 6.52 ,&,density D = 4.30 g ~m-~[l]).Thisinterestisgenerated,inpart, byacombination of the quasi-one-dimensionality and non-collinear magnetic structure of this antiferromagnet, which result in a non-trivial magnetic phase diagram [2].In accordance with data obtained in elastic neutron diffraction experiments [3], CsMnBr, has, for H = 0 and below the three-dimensional magnetic ordering temperature T, = 8.32 K, a stacked triangular structure with spins lying in the basal easy

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The antiferromagnetic resonance in thin single-crystal plates of MnCO, was studied at wd2x = 9.3 GHz and T = 4.2-10 K for large values of the angle B between the static magnetic field Hand the basal plane of the crystals. A set of quasi-equidistant absorption lines was observed for a wide range of magnetic fields H. which can be attributed to the size effect: the resonances of plane spin-waves with different wavevector values, Ikl= 1O'cm' I. standing perpendicularly to the crystal plate. The relaxation of the spin-waves was evaluated from the width of individual resonance lines, and found to amount to Aw,/2x = 0.03MHzat T = 4 . 2 K .

A neutron scattering study of the quasionedimensional, dilute Isinglike antiferromagnet CsCo0.83Mg0.17Br3

The parametric excitation of spin-waves was studied in the easy-plane antiferromagnet MnCO3 at a microwave pumping frequency wP/2r = 33.8 GHz and T = 1.6 K. The experiments were performed for oblique orientation of the magnetic field H with respect to the basd plane of the crystal. W e found that the two &Rerent microwave threshold fields for the appearance ( & I ) and disappearance (h,z) of parmetric excitation aa well as the 'coefficient of hardness' IC = (&I -hC*)/&x strongly depend on the angle 9 between H and the basal plane, showing a decrease with increasing 9. Our experimental results can be explained by the assumption that some part of the spin-wave relaxation and hardness effect arise from an interaction of spin-waves with 'orthogonal' magnetic impurities.