Virtual spin-wave state below and above the Curie-temperature in a dilute Fe(Cr) alloy

Some of the consequences of a recently proposed first-order decoupling are examined in the Green function theory of a [Formula: see text] Heisenberg antiferromagnet. The low-temperature magnetization differs in terms proportional to T4 from Oguchi's spin wave formula. The Neél temperature is equal to the R.P.A, Curie temperature.

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Study of Magnetism of Two-Dimensional Ferromagnetic Graphene

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.601.89 ◽

2012 ◽

Vol 601 ◽

pp. 89-93

Author(s):

Bin Zhou Mi ◽

Yong Hong Xue ◽

Huai Yu Wang ◽

Yun Song Zhou ◽

Xiao Lan Zhong

Keyword(s):

Curie Temperature ◽

Quantum Number ◽

Spin Wave ◽

Wave Energy ◽

Spontaneous Magnetization ◽

Exchange Parameter ◽

Magnetic Nanomaterials ◽

Two Dimensional ◽

Spin Quantum ◽

Spin Quantum Number

In this paper, the magnetic properties of ferromagnetic graphene nanostructures, especially the dependence of the magnetism on finite temperature, are investigated by use of the many-body Green’s function method of quantum statistical theory. The spontaneous magnetization increases with spin quantum number, and decreases with temperature. Curie temperature increases with exchange parameter J or the strength K2 of single-ion anisotropy and spin quantum number. The Curie temperature TC is directly proportional to the exchange parameter J. The spin-wave energy drops with temperature rising, and becomes zero as temperature reaches Curie temperature. As J(p,q)=0, ω1=ω2, the spin wave energy is degenerate, and the corresponding vector k=(p, q) is called the Dirac point. This study contributes to theoretical analysis for pristine two-dimensional magnetic nanomaterials that may occur in advanced experiments.

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SUPERCONDUCTIVITY FROM SPIN-WAVE EXCITATIONS NEAR THE FERROMAGNETIC AND ANTIFERROMAGNETIC INSTABILITIES

International Journal of Modern Physics B ◽

10.1142/s0217979205027974 ◽

2005 ◽

Vol 19 (01n03) ◽

pp. 77-85

Author(s):

Y. M. MALOZOVSKY ◽

J. D. FAN

Keyword(s):

Spin Wave ◽

P Wave ◽

Wave State ◽

Spin Wave Excitations ◽

T Matrix ◽

D Wave

We study pairing by the exchange of spin-wave excitations near the ferromagnetic or antiferromagnetic instability in terms of the effective two-particles T-matrix. We show that near the ferromagnetic instability the paring due to the exchange of the paramagnetic excitations can occur in the p-wave state (ℓ=1) and m=±1. We show that near the antiferromagnetic instability the pairing due to the exchange by the paramagnetic excitations occurs also in the p-wave state (ℓ=1) but with m=0 and that there is no pairing in d-wave state.

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Magnetization of magnetically inhomogeneous Sr2FeMoO6-δ nanoparticles

Modern Electronic Materials ◽

10.3897/j.moem.7.3.75786 ◽

2021 ◽

Vol 7 (3) ◽

pp. 85-90

Author(s):

Gunnar Suchaneck

Keyword(s):

Curie Temperature ◽

Temperature Dependence ◽

Magnetic Materials ◽

Spin Wave ◽

Analytical Description ◽

Higher Order ◽

Ferromagnetic Behavior ◽

Double Perovskites ◽

Langevin Function ◽

First Time

Magnetization is a key property of magnetic materials. Nevertheless, a satisfactory, analytical description of the temperature dependence of magnetization in double perovskites such as strontium ferromolybdate is still missing. In this work, we develop, for the very first time, a model of the magnetization of nanosized, magnetically inhomogeneous Sr2FeMoO6-δ nanoparticles. The temperature dependence of magnetization was approximated by an equation consisting of a Bloch-law spin wave term, a higher order spin wave correction, both taking into account the temperature dependence of the spin-wave stiffness, and a superparamagnetic term including the Langevin function. In the limit of pure ferromagnetic behavior, the model is applicable also to SFMO ceramics. In the vicinity of the Curie temperature (T/TC > 0.85), the model fails.

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