Commensurate and incommensurate states of a spin density wave in a quasi-two-dimensional system with an anisotropic energy spectrum in an external magnetic field of arbitrary direction relative to magnetization

Journal Article · Mon Apr 15 04:00:00 EDT 2013 · Journal of Experimental and Theoretical Physics

DOI:https://doi.org/10.1134/S1063776113040080· OSTI ID:22126552

Ursu, V. A. ^[1]

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1. Academy of Sciences of Moldova, Institute of Applied Physics (Moldova, Republic of)

A theory of thermodynamic properties of a spin density wave (SDW) in a quasi-two-dimensional system (with a preset impurity concentration x) is constructed. We choose an anisotropic dispersion relation for the electron energy and assume that external magnetic field H has an arbitrary direction relative to magnetic moment M{sub Q}. The system of equations defining order parameters M{sub Q}{sup z}, M{sub Q}{sup {sigma}}, M{sub z}, and M{sup {sigma}} is constructed and transformed with allowance for the Umklapp processes. Special cases when H Double-Vertical-Line M{sub Q} and H Up-Tack M{sub Q} (H{sub Z}H{sup {sigma}} = 0) are considered in detail as well as cases of weak fields H of arbitrary direction. The condition for the transition of the system to the commensurate and incommensurate states of the SDW is analyzed. The concentration dependence of magnetic transition temperature T{sub M} is calculated, and the components of the order parameter for the incommensurate phase are determined. The phase diagram (T,{approx}x) is constructed. The effect of the magnetic field on magnetic transition temperature T{sub M} is analyzed for H{sub Z}H{sup {sigma}} = 0, and longitudinal magnetic susceptibility {chi} Double-Vertical-Line is calculated; this quantity demonstrates the temperature dependence corresponding to a system with a gap for x < x{sub c} and to a gapless state for x > x{sub c}. In the immediate vicinity of the critical impurity concentration (x {approx} x{sub c}), the temperature dependence of the magnetic susceptibility acquires a local maximum. The effect of anisotropy of the electron energy spectrum on the investigated physical quantities is also analyzed.

• OSTI ID: 22126552
• Journal Information: Journal of Experimental and Theoretical Physics, Journal Name: Journal of Experimental and Theoretical Physics Journal Issue: 4 Vol. 116; ISSN JTPHES; ISSN 1063-7761
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANISOTROPY
CONCENTRATION RATIO
DISPERSION RELATIONS
ENERGY SPECTRA
IMPURITIES
MAGNETIC FIELDS
MAGNETIC MOMENTS
MAGNETIC SUSCEPTIBILITY
MAGNETIZATION
ORDER PARAMETERS
PHASE DIAGRAMS
SPIN WAVES
TEMPERATURE DEPENDENCE
TRANSITION TEMPERATURE
TWO-DIMENSIONAL CALCULATIONS
UMKLAPP PROCESSES