Spin Wave Analysis of the Two‐Dimensional Heisenberg Antiferromagnets Rb₂MnCl₄ and (CH₃NH₃)₂MnCl₄

Abstract

The frequencies are measured of the magnetic excitations (magnons) of Rb,MnCl, and (CH,NH,),MnCI, b y means of inelastic neut'ron scattering for [c, 0, 01 at 8 K and by magnetic resonance techniques for k = 0 a t various temperatures. From the temperature dependence of the intensity of a magnetic Bragg peak, experimentalvalues arcobtained for the sublatticemagnetizationof those two 2D Heisenberg antiferromagnets. The experimental dataare analyzedtheoretically within the framework of Oguchi's renormalized spin wave theory. The spin wave parameters (exchange field and anisotropy field) are extracted from the measured magnon frequencies in a self-consistent way. They are utilized t o calculate not only magnon dispersion curvcs but also other magnetic properties as the sublattice magnetization and the magnetic susceptibility. Except for the Susceptibility, the calculated values compare well with experimental data in the temperature range 0 5 T 5 0.7 T s .Die Frequenzen der magnetischen Anregungen (Magnonen) von Rb,MnCl, und (CH,NH,),MnC14 werden gemessen, und zwar mittels inelastischer Keut.ronenstreuung fur [E, 0, 01 bei einer Temperatur van 8 K und mittels einer magnetischen Resonanztechnik fur k = 0 bei einer Reihe van Temperaturen. Aus der Temperaturabhangigkeit eines magnetischen Bragg-Reflexes werden experimentelle Werte fur die Untergittermagnetisierung dieser beiden 2D-Heisenberg-Antiferromagneten ermittelt. Die experimentellen Ergebnisse werden dann einer theoretischen Analyse ini Rahmen der renormalisierten Spinwellentheorie Ton Oguchi unterzogen. Die Spinwellenparameter (Austauschfeld und Anisotropiefeld) merden in selbstkonsistenter Weise aus den gemessenen Magnonenfrequenzen ermittelt. Sie werden dann dazu benutzt, nicht nur die Magnondispcrsionskurven, sondern auch anderc GroBen wie die Untergittermagnetisierung und die magnet ische Suszeptibilitat zu berechnen. Mit Ausnahme dcr Suszeptibilitlt stimmen die berechneten und experimentellen Werte im Temperaturbereich 0 5 T 5 0,7 T , recht gut uberein.

Magnetic properties and critical behavior of the pure and diluted two-dimensional weak ferromagnet (CH3NH3)2Mn1−xCdxCl4

“…The exponent ␤ 1 determined for tϾ0.01 in CH 3 MnCl is consistent with the value ␤ϳ0.18 obtained for the sublattice magnetization from neutron diffraction experiments in the same range of t. 7 Our data covers, however, a region closer to T N where the crossover is revealed. A value for the ␤ exponent close to ours was observed in Cu(HCOO) 2 4H 2 O (␤ϭ0.22), a nearly 2D system that at the 3D ordering exhibit also a canted structure.…”

“…1 the data are also compared with the behavior of the sublattice magnetization of CH 3 MnCl measured with neutron diffraction ͑open square symbols͒. 7 As is clearly seen in the overall they have the same behavior, as is expected. The occurrence of canting in this class of compounds is allowed because the lack of center of symmetry between the manganese ions.…”

Inter‐Sublattice Energy Transfer in Rb2MnCI4 Antiferromagnetic Crystals

“…Here we investigate experimentally the LB of Rb,MnCI, to clarify whether the Ising-type antiferromagnetism, which has been suggested from neutron scattering [2,3], is observable in Rb,MnCl,. Additionally we examine the luminescence to try to know whether a correlation between luminescence and magnetism ( e g magnetic short-range order) exists.…”

Magnetization steps in the diluted Heisenberg layer materials(CH3NH3)2Paduan-Filho1, Gratens2, Bindilatti3 et al. 2005Phys. Rev. B2070View full textAdd to dashboardCite

“…For pure MAMC ͑x =1͒ the best values for J 1 / k B are probably from the two analyses of inelastic neutron scattering data, i.e., −4.69 K and −4.80 K. 18 The slightly lower value obtained in the present work is for x Ͻ 0.3. The difference is apparently due to a decrease of J 1 with decreasing x.…”

“…18 The results were J / k B = −4.80 K from "simple spin wave theory," and −4.69 K from "renormalized spin-wave theory." This J was identified as the nearest-neighbor ͑NN͒ in-plane exchange constant J 1 .…”