Ordering in ferromagnets with random anisotropy
- 1 January 1986
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 33 (1), 251-261
- https://doi.org/10.1103/physrevb.33.251
Abstract
We summarize and extend our study (using real-space response and correlation functions) of the properties of a continuous-symmetry ferromagnet with random anisotropy, distinguishing between the cases of weak and strong random anisotropy. For the weak-anisotropy case we find three different magnetic regimes, according to the strength of the external magnetic field H. In zero H, the net magnetization is zero, although the ferromagnetic correlation length (FCL) is large. We call a ferromagnet in this first regime a correlated spin glass (CSG). It has a very large magnetic susceptibility, and hence a relatively small coherent anisotropy converts it into a nearly typical ferromagnetic domain structure. Also, a relatively small magnetic field nearly aligns the CSG, producing the second regime, which we call a ferromagnet with wandering axis (FWA). The FWA is a slightly noncollinear structure in which the tipping of the magnetization with respect to the field varies over the system. The tipping angle is correlated over a (field-dependent) correlation length which is smaller than the FCL of the CSG. As the field increases the correlation length in the FWA decreases, until the third regime is reached, wherein the tipping angles (which are smaller than in the FWA) are completely uncorrelated from site to site. We obtain the magnetization or susceptibility (as appropriate) for each of these three regimes. We also show that the temperature dependence of the (single-ion) random anisotropy strength can provide a plausible explanation for certain classes of reentrant phenomena and susceptibility cusps observed in magnetization studies. Neutron scattering studies appear to be consistent with the predicted dependence of the FCL in the FWA regime, and display the expected rise of the FCL in the CSG regime as the random anisotropy strength decreases with increasing temperature.
Keywords
This publication has 35 references indexed in Scilit:
- Statics and dynamics of spin and electric dipoles in three, four, and other dimensionsPhysical Review B, 1985
- Magnetic properties of solids with small random anisotropyJournal of Magnetism and Magnetic Materials, 1984
- Phenomenological theory of amorphous magnets with small random anisotropyJournal of Physics C: Solid State Physics, 1983
- Spin-glass and ferromagnetic states in amorphous solidsPhysical Review B, 1982
- The influence of spatially random magnetostatic, magnetocrystalline, magnetostrictive and exchange fluctuations on the law of approach to ferromagnetic saturation of amorphous ferromagnetsJournal of Magnetism and Magnetic Materials, 1978
- Random anisotropy in amorphous ferromagnetsJournal of Applied Physics, 1978
- Amorphous magnetic orderJournal of Applied Physics, 1978
- Spin-Glass and Ferromagnetic Behavior Induced by Random Uniaxial AnisotropyPhysical Review Letters, 1978
- Initial magnetization, remanence, and coercivity of the random anisotropy amorphous ferromagnetPhysical Review B, 1977
- Random-Field Instability of the Ordered State of Continuous SymmetryPhysical Review Letters, 1975