Journal ArticleDOI
Ordering in ferromagnets with random anisotropy.
TLDR
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.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 ${H}^{\mathrm{\ensuremath{-}}1/2}$ 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.read more
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Journal ArticleDOI
Some aspects of the theory of spin glasses and disordered ferromagnets
I.A. Akhiezer,D.P. Belozorov +1 more
TL;DR: In this paper, the transition from the metastable to the stable ground state of a spin glass with anisotropy is discussed within the scope of the phenomenological theory of spin glass behavior.
Journal ArticleDOI
Effect of ball milling and dynamic compaction on magnetic properties of Al2O3/Co(P) composite particles
Elena Denisova,L. A. Kuzovnikova,Rauf S. Iskhakov,A. A. Bukaemskiy,Evgeniy Eremin,Ivan V. Nemtsev +5 more
TL;DR: In this article, the magnetic properties of composite Al2O3/Co(P) particles during ball milling and dynamic compaction were investigated, and the magnetic and structural properties of the composite particles were characterized by scanning electron microscopy, X-ray diffraction and the use of the Physical Property Measurement System.
Journal ArticleDOI
Transition behavior in Gd‐Co based alloys with strong anisotropy
K. M. Lee,Michael J. O'Shea +1 more
TL;DR: In this article, the effect of random magnetic anisotropy (RMA) on transition behavior in Gd•Co glasses was studied and it was shown that the large RMA induced by alloying with anisotropic rare earth elements produces standard speromagnetic behavior which includes nonsaturation at large enough concentrations at 4.2 K and high fields in all the alloys except the most concentrated Tb alloys.
Journal ArticleDOI
Nonlinear and thermal effects in the absorption of microwaves by random magnets
TL;DR: In this article , the temperature dependence of the absorption of microwaves by random-anisotropy magnets was studied and it was shown that on increasing the power, heating and over-barrier spin transitions come into play, resulting in the nonlinear behavior.
Journal ArticleDOI
High performance magnetic materials produced by assembling gas-phase magnetic nanoclusters
TL;DR: In this paper, the magnetic properties of supported Fe nanoclusters containing a few hundred atoms and coated with Co or embedded in Ag matrices have been studied using XMCD and magnetometry.
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