Ferromagnetic moment and antiferromagnetic coupling in (Ga,Mn)As thin films

Edmonds, K. W.; Farley, N. R. S.; Johal, T. K.; Laan, G. van der; Campion, R. P.; Gallagher, B. L.; Foxon, C. T.

doi:10.1103/physrevb.71.064418

Cited by 112 publications

(116 citation statements)

References 29 publications

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“…Previous results on x-ray absorption spectroscopy [52][53][54] have shown that the existence of local moments may cause the observed multiplet structures resulting from the interaction of the core hole with the excited electron, thus, representing a final-state effect. The same has also been observed for the case of XPS.…”

Section: Resultsmentioning

confidence: 99%

Exchange coupling in the correlated electronic states of amorphous GdFe films

et al. 2013

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The bulk sensitivity of hard x-ray photoelectron spectroscopy in combination with circularly polarized radiation of the P09 beamline at PETRA III enables the investigation of the magnetic properties of capped films. We have determined the temperature dependence of the magnetic circular dichroism in the Fe 2p and in the Gd 3d states in amorphous GdFe films. The magnetic dichroism reflects the stronger temperature dependence of Gd moments compared to Fe moments in agreement with mean-field models. We resolved the exchange split Gd 3d 5/2 substates and found a significant temperature dependence of the splitting which is attributed to a temperature dependent part of the exchange energy caused by Stoner-like itinerant states. A comparison of experimental and simulated x-ray photoemission spectra with corresponding data for x-ray absorption spectroscopy exciting the identical core holes clearly demonstrates that the core hole exchange interaction is the origin of the observed multiplet features for Gd.

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Section: Resultsmentioning

confidence: 99%

Exchange coupling in the correlated electronic states of amorphous GdFe films

et al. 2013

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“…1 The existence of well-established magneto-optical sumrules that allow to obtain the spin and orbital contribution to the magnetic moment directly from the integral of the spectra 2-4 made it an essential technique to study the magnetic properties of matter. These sumrules are widely and successfully applied at spin-orbit split L 2 ,3 -edges of transition metals [5][6][7][8] and M 4 ,5 -edges of actinides. 9 On the other hand, in the absence of spinorbit splitting of the core state (as for K -or L 1 -edge), only the orbital magnetization sum-rule 2,4 can apply and a quantitative analysis of the spectra is far from being straightforward.…”

Section: Introductionmentioning

confidence: 99%

X-ray magnetic and natural circular dichroism from first principles: Calculation of K - and L1 -edge spectra

et al. 2017

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An efficient first principles approach to calculate X-ray magnetic circular dichroism (XMCD) and X-ray natural circular dichroism (XNCD) is developed and applied in the near edge region at the K -and L1 -edges in solids. Computation of circular dichroism requires precise calculations of X-ray absorption spectra (XAS) for circularly polarized light. For the derivation of the XAS cross section, we used a relativistic description of the photon-electron interaction that results in an additional term in the cross-section that couples the electric dipole operator with an operator σ · ( × r) that we name spin-position. The numerical method relies on pseudopotentials, on the gauge including projected augmented wave method and on a collinear spin relativistic description of the electronic structure. We apply the method to the calculations of K -edge XMCD spectra of ferromagnetic iron, cobalt and nickel and of I L1 -edge XNCD spectra of α-LiIO3, a compound with broken inversion symmetry. For XMCD spectra we find that, even if the electric dipole term is the dominant one, the electric quadrupole term is not negligible (8% in amplitude in the case of iron). The term coupling the electric dipole operator with the spin-position operator is significant (28% in amplitude in the case of iron). We obtain a sum-rule relating this new term to the spin magnetic moment of the p-states. In α-LiIO3 we recover the expected angular dependence of the XNCD spectra.

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“…So far, several results of XMCD measurements on Ga 1−x Mn x As have been reported [6,7,8]. From H dependent XMCD studies, the enhancement of XMCD intensity by post-annealing implies AF interaction between the Mn sub and Mn int ions [8].…”

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Nature of Magnetic Coupling between Mn Ions in As-GrownGa1−xMnxAsStudied by X-Ray Magnetic Circular Dichroism

et al. 2008

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The magnetic properties of as-grown Ga1−xMnxAs have been investigated by the systematic measurements of temperature and magnetic field dependent soft x-ray magnetic circular dichroism (XMCD). The intrinsic XMCD intensity at high temperatures obeys the Curie-Weiss law, but residual spin magnetic moment appears already around 100 K, significantly above Curie temperature (TC), suggesting that short-range ferromagnetic correlations are developed above TC. The present results also suggest that antiferromagnetic interaction between the substitutional and interstitial Mn (Mnint) ions exists and that the amount of the Mnint affects TC.PACS numbers: 75.50. Pp, 78.70.Dm, 75.25.+z, 79.60.Dp Ga 1−x Mn x As is a prototypical and most wellcharacterized diluted magnetic semiconductor (DMS) [1]. Because Ga 1−x Mn x As is grown under thermal nonequilibrium conditions, however, it is difficult to avoid the formation of various kinds of defects and/or disorder. In fact, Rutherford backscattering (RBS) channeling experiments for as-grown Ga 0.92 Mn 0.08 As samples has shown that as many as ∼ 17 % of the total Mn ions may occupy the interstitial sites [2]. It is therefore supposed that antiferromagnetic (AF) interaction between the substitutional Mn (Mn sub ) ions and interstitial Mn (Mn int ) ions may suppress the magnetic moment [3,4]. In addition, the random substitution of Mn ions may create inhomogeneous Mn density distribution, which may lead to the development of ferromagnetic domains above Curie temperature (T C ) [5]. The characterization of non-ferromagnetic Mn ions is therefore a clue to identify how they are related with the ferromagnetic ordering and eventually to improve the ferromagnetic properties of Ga 1−x Mn x As samples. However, it has been difficult to extract the above information through conventional magnetization measurement due to the large diamagnetic response of the substrate and the unavoidable mixture of magnetic impurities.X-ray magnetic circular dichroism (XMCD), which is an element specific magnetic probe, is a powerful technique to address the above issues. So far, several results of XMCD measurements on Ga 1−x Mn x As have been reported [6,7,8]. From H dependent XMCD studies, the enhancement of XMCD intensity by post-annealing implies AF interaction between the Mn sub and Mn int ions [8]. In the present study, in order to characterize the magnetic behaviors of the Mn sub and Mn int , we have extended the approach and performed systematic temperature (T ) and magnetic field (H) dependent XMCD studies in the Mn L 2,3 absorption edge region of Ga 1−x Mn x As. We have found that short-range ferromagnetic correlations develop significantly above T C and that AF interaction between the Mn sub and Mn int is important to understand the magnetic properties of Ga 1−x Mn x As.We prepared two as-grown samples with different Mn concentrations; x = 0.042 and 0.078, whose T C was ∼ 60 and 40 K, respectively, as determined by an Arrott plot of the anomalous Hall effect. To avoid surface oxidation, the sample had...

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Ferromagnetic moment and antiferromagnetic coupling in (Ga,Mn)As thin films

Cited by 112 publications

References 29 publications

Exchange coupling in the correlated electronic states of amorphous GdFe films

Exchange coupling in the correlated electronic states of amorphous GdFe films

X-ray magnetic and natural circular dichroism from first principles: Calculation of K - and L1 -edge spectra

Nature of Magnetic Coupling between Mn Ions in As-GrownGa1−xMnxAsStudied by X-Ray Magnetic Circular Dichroism

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