Thickness dependent magnetic properties of (Ga,Mn)As ultrathin films

Abstract

We report on a monotonic reduction of Curie temperature in dilute ferromagnetic semiconductor (Ga,Mn)As upon a well controlled chemical-etching/oxidizing thinning from 15 nm down to complete removal of the ferromagnetic response. The effect already starts at the very beginning of the thinning process and is accompanied by the spin reorientation transition of the in-plane uniaxial anisotropy. We postulate that a negative gradient along the growth direction of self-compensating defects (Mn interstitial) and the presence of surface donor traps gives quantitative account on these effects within the p–d mean field Zener model with adequate modifications to take a nonuniform distribution of holes and Mn cations into account.

Three-dimensional Heisenberg critical behavior in the highly disordered dilute ferromagnetic semiconductor (Ga,Mn)As

“…However, the interstitial Mn is relatively mobile and can be removed by low temperature annealing [40] to produce material in which the carrier and moment compensation is very low [41]. As-grown (Ga,Mn)As has a gradient in the interstitial Mn concentration in the growth direction due to partial annealing during MBE growth and a corresponding gradient in T C [42]. The samples used in these studies were annealed in air for 48 hours at 180°C, a procedure which has been shown to increase the homogeneity [43] and the critical temperature T C [17].…”

Magnetoelectric effect in GaMnAs /P(VDF-TrFE) composite multiferroic nanostructures

“…2 curves a,b,c) to an insulating (curve d) behavior. The T C lowering with further decreasing of GaMnAs thickness is due to the presence of antisite As Ga donors in the low-temperature grown LTeGaAs buffer layer, which reduces the hole concentration in adjacent GaMnAs channel and also, due to a built-in negative gradient of the Mn interstitials, which provide the antiferromagnetic interactions with the substitutional Mn ions [12]. Fig.…”

On the nature of the Mn-related states in the band structure of (Ga,Mn)As alloys via probing the E1 and E1 + Δ1 optical transitions

“…18 From SE measurements, the spectral dependences of the ellipsometric angles WðkÞ and D(k) are obtained, which enable to calculate the effective complex dielectric function e 1 þ ie 2 . In order to obtain the ðe 1 ; e 2 Þ spectra of a near-surface layer of a sample one has to create a sample structure model of the investigated layered material, 19 containing such parameters as thicknesses, compositions, and pseudo dielectric functions of the substrate and the neighboring layers.…”

“…This assumption is supported by previous studies on the oxide chemical etching of (Ga,Mn)As epitaxial layers. 18,23,24 The pseudo dielectric functions of (Ga,Mn)As layers have been obtained by means of the least squares fit of the excitonic features E 1 and E 1 þ D 1 described by a Lorentzian oscillators previously used in Ref. 10 and using a simple two phase layer/substrate model of the heterostructures.…”