Exchange interactions and magnetism ofCo2+inZn1−

Abstract

A study of cobalt-carrier exchange interactions is carried out in very dilute Zn 1Ϫx Co x Te ͑xр1%͒ from correlated magneto-optical and magnetization measurements at Tϭ1.8 K. The resonant magneto-optic Kerr effect is used to complement magnetoreflectance experiments, and determine precisely the exciton Zeeman splittings on single crystals of various Co compositions. Correlated measurements of magnetization performed on the same samples provide a determination of exchange integrals for ⌫ 6 and ⌫ 8 bands within the framework of the exchange model based on the mean-field approximation. In the investigated field and composition range, we find N 0 ␣ϭ0.31Ϯ0.03 eV; N 0 ␤ϭϪ3.03Ϯ0.15 eV. This abnormally large value of the p-d exchange constant does not vary with Co concentration in the investigated region. Low-temperature magnetization data obtained in fields up to 15 T are consistently interpreted in a model including the contributions of isolated ions and Co 2ϩ -Co 2ϩ pairs of second and third neighbors for the values of exchange constants previously determined. Antiferromagnetic interactions between more distant ions than third neighbors are also taken into account. The long-range exchange parameters obtained by using either a modified Brillouin function or a mean-field approach are in good agreement.

Magnetic circular dichroism spectroscopy of Co2+:CdS diluted magnetic semiconductor quantum dots

“…The quantity N 0 α, on the other hand, is anticipated to be small due to the lack of unpaired spin in the nonbonding e orbitals of Co 2+ , and has been shown to be 10 -100 times smaller in magnitude than N 0 β in cobalt-doped CdTe bulk single crystals. [35][36][37] From Figure 9, the polarity of the MCD psuedo-A signal can be directly related to the sense of the Γ 8 valence band splitting, and hence to the sign of N 0 β. This feature will be positive when N 0 β < 0, the scenario illustrated in Figure 9.…”

Structural, magnetic and optical properties of Co-diffused CdTe thin films

“…Magnetic properties of Co based CdTe materials have been studied previously [2][3][4] and it is reported the large p-d interaction and d-d exchange interaction for Co 2+ [10][11][12]. However, to date, most of the studies based on single crystals and doping effect of Co in CdTe samples.…”

Nickel-Based Diluted Magnetic Semiconductor (Zn, Ni)Te

“…where x eff is an effective value and the last term is the intrinsic splitting in ZnTe with the effective g-factor g * g e þ 6j ¼ À0:8 [7]. We assume a typical value for the conduction band exchange parameter, N 0 a ¼ 0:2 eV.…”