In order to study the magnetic properties of amorphous matter Gubanov (1) considered a mean structure of atoms and concluded that a finite Curie temperature may exist. In this letter we get an expression for the reduced spontaneous mag- Our model shows that ferromagnetism does not require crystal structure.Starting from a Heisenberg model for a given arbitrary structure we get for the mean value of the spin of atom i in the molecular field approximation. We assume for simplicity that Si = S and gi = g. T > Tc: Noting that Bs(x) = F x for small x, the summation of equation (1) over i and the averaging with the spatial distribution function fN("Y1, W2, . . . 1) A more detailed variant will be published later.

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The influence of extended stochastic structure fluctuations on the self‐energy and damping of long‐wavelength magnons in amorphous ferromagnets is investigated within the Heisenberg model. By improving the Matsubara‐Kaneyoshi formalism (MKF) the magnon energy in “improved quasi‐crystalline” approximation is derived as a start approximation in the equation of motion for the Green's function, thus containing already important structural information. The typical static structure factor in the small‐angle region is approximated by convenient analytical model functions. We derive the renormalization R(q) of the stiffness constant D and the magnon damping Γ(q), where the latter shows a characteristic q5‐behaviour in the small‐q range that can be explained by “magnetic Rayleigh‐scattering” due to the magnetic inhomogeneities acting as “point defects” for long‐wavelength magnons. In the larger‐q range the magnon damping, in agreement with other authors, is found to obey a q3‐law. The general behaviour of the renormalization R(q) for long‐wavelength magnons is found to be similar for all model functions used for the static structure factor. Linear extrapolation of Dq2R(q) from the larger‐q region supplies an apparent gap energy due to the amorphous structure (independent from the magnetic dipole–dipole interaction, which is neglected in this paper). The explanation of this apparent gap energy is given by “compensational magnons” that accompany the magnon, compensating the inhomogeneities, thus forming a “magnon‐dressed” magnon.

Amorphous systems with antiferromagnetic interactions (e.g. glasses containing high concentrations of transition elements (1, 2) and ferrimagnetic rare earth-transition metal amorphous films for bubble devices (3, 4)) have been the subject of several investigations. Nevertheless up to now the existence of amorphous antiferromagnetism i s a controversial point (5, 6) because of the high degree of misfit: Due to the structural disorder it is not possible to surround a plus spin by minus spins only or vice versa. By artificially suppressing the misfit the simple sublattice model of amorphous antiferromagnets (7 to 9) favours an antiferromagnetic order in an inadmissible way.We have simulated a kind of hard sphere gas. Hard disks, positions of which are chosen a s random numbers, a r e put into a two-dimensional box. Periodical boundary conditions a r e used (Fig. 1). Within the Ising model with the Hamiltonian H = -> Iij(r)srsjz i < j we have calculated that spin configuration which belongs to the lowest energy (ground state) for the case S = 1/2 and I. .(r) < 0. 11The result i s shown in Fig. 1 for 2 3 spins and a distance dependend exchange interaction a s given in Fig. 2b. 5 physica (b)