Magnetic interactions in dilute magnetic semiconductors

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7205453

Vu, T Q

A study of various magnetic phenomena in the II-VI dilute magnetic semiconductors is presented. Materials used for the study were Zn[sub 1[minus]x]Co[sub x]Te, Cd[sub 1[minus]x]Co[sub x]S, Cd[sub 1[minus]x]Fe[sub x]S, and Cd[sub 1[minus]x]Fe[sub x]Se. Various magnetometric techniques were employed for the study. Cubic zincblende Zn[sub 1[minus]x]Co[sub x]Te was used to study magnetization steps due to distant neighbors. The author observed magnetization steps due to antiferromagnetic exchange interactions J[sub ij]S[sub i]S[sub j] between pairs of second- and third-neighbor magnetic ions. The values of the second, J[sub 2]/k[sub B] and third, J[sub 3]/k[sub B], exchange constants were determined to be [minus]5.7 [+-] 0.6 and [minus]2.7 [+-] 0.3 K, respectively. The results are compared with various models for the distance dependence of J[sub i]. The wurtzite Cd[sub 1[minus]x]Co[sub x]S was used to study various effects resulting from the single-ion anisotropy DS[sup 2][sub x] of the Co[sup ++] ion. The size of the single-ion anisotropy constant D in the wurtzite Cd[sub 1[minus]x]Co[sub x]S was determined using a novel magnetization step method. D/k[sub B] = 0.96 [+-] 0.02 K was obtained. The effects of the single-ion anisotropy on the magnetization steps due to pairs of magnetic ions were theoretically investigated. Analytical solutions for the pair Hamiltonian for the configuration H parallel c were found. Numerical results for the configuration H perpendicular c were also obtained. In the Fe based DMS, the ground state of Fe[sup ++] is a singlet. For the wurtzite Cd[sub 1[minus]x]Fe[sub x]S and Cd[sub 1[minus]x]Fe[sub x]Se, a reversal of magnetic anisotropy at high fields was observed. To find an explanation for this phenomenon, the author solved numerically the static crystal-field Hamiltonian for an isolated Fe[sup ++]. The calculations did quantitatively predict the reversal.

• Research Organization: Tufts Univ., Medford, MA (United States)
• OSTI ID: 7205453
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360606* -- Other Materials-- Physical Properties-- (1992-)
665000 -- Physics of Condensed Matter-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
ANISOTROPY
ANTIFERROMAGNETISM
CADMIUM COMPOUNDS
CADMIUM SELENIDES
CADMIUM SULFIDES
CHALCOGENIDES
COBALT COMPOUNDS
COBALT SULFIDES
COBALT TELLURIDES
CRYSTAL FIELD
DOMAIN STRUCTURE
EXCHANGE INTERACTIONS
HAMILTONIANS
INORGANIC PHOSPHORS
INTERACTIONS
INTERMETALLIC COMPOUNDS
IRON COMPOUNDS
IRON SELENIDES
IRON SULFIDES
MAGNETIC PROPERTIES
MAGNETIC SEMICONDUCTORS
MAGNETISM
MAGNETIZATION
MATERIALS
MATHEMATICAL OPERATORS
PHOSPHORS
PHYSICAL PROPERTIES
PHYSICS
QUANTUM OPERATORS
SELENIDES
SELENIUM COMPOUNDS
SEMICONDUCTOR MATERIALS
SOLID STATE PHYSICS
SULFIDES
SULFUR COMPOUNDS
TELLURIDES
TELLURIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
ZINC COMPOUNDS
ZINC TELLURIDES