THEORY OF THE EFFECTS OF ANISOTROPY ON SPIRAL SPIN-CONFIGURATIONS WITH APPLICATION TO RARE EARTH METALS

Journal Article · Thu Mar 01 04:00:00 EST 1962 · J. Phys. Soc. Japan

OSTI ID:4646661

Kaplan, T A

Some effects of anisotropy on spirals are studied by considering a spin- hamiltonian that includes exchange forces, crystal field and dipolar forces. It is shown that the ferromagnetic spiral (FS) observed in Er at low temperatures can be the ground state provided terms of at least fourth order in the spin variables are present in the hamiltonian. Furthermore, the observed cone angles can be realized with anisotropy forces much smaller than the exchange forces. The spin wave spectrum for the FS has the properties that omega (k) is linear in k for small k, and there are two distinct branches, as contrasted with the case of simple spirals. For high temperatures, calculations are made on the basis of the molecular field approximation. It is shown that a small easy axis anisotropy implies that at the highest transition temperature, T/sub c/, the ordered spin configuration is a static longitudinal spin wave as observed in Er. As T decreases below T/sub c/ the amplitude of this wave grows in order (T/sub c/ - T)/ sup 1/2/ with odd harmonics appearing in order (T/sub c/- T)/sup 3/2/. The transverse components remain zero until a second transition temperature is reached, below which they begin to order. The observed thermal variation in wavelength can be accounted for in Er specifically by the dipolar forces. (auth)

• Research Organization: Massachusetts Inst. of Tech., Lexington
• NSA Number: NSA-17-037770
• OSTI ID: 4646661
• Journal Information: J. Phys. Soc. Japan, Journal Name: J. Phys. Soc. Japan Vol. Vol: 17: Suppl. B-I
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ANISOTROPY
CONFIGURATION
CRYSTALS
DIFFERENTIAL EQUATIONS
DIPOLES
ELECTRIC FIELDS
ENERGY LEVELS
ERBIUM
FERROMAGNETIC MATERIALS
HAMILTONIAN
INTERACTIONS
LATTICES
MAGNETISM
MOLECULES
NUMERICALS
PHYSICS
RARE EARTHS
SPECTRA
SPECTRAL SHIFT
SPIN
SPIN WAVES
TEMPERATURE
TRANSIENTS
TRANSITION TEMPERATURE