Photon Factory Activity Report 2004 #22 Part B (2005)
Electronic Structure of Condensed Matter

11A/2004G206

X-ray Magnetic Circular Dichroism study of MnGeP2 thin filmYoshitaka OSAFUNE*1, Yukiaki ISHIDA1, Jong-Il HWANG1, Masaki KOBAYASHI1,Atsushi FUJIMORI1, Kazutoshi MAMIYA2, Hiroyuki TOKANO3, Tsuneharu KOIDE2,Kazuyuki MINAMI4, Takayuki ISHIBASHI4, and Katsuaki SATO4
1
Department of Physics and Department of Complexity Science and Engineering,
University of Tokyo, Kashiwa 277-8561, Japan2
Photon Factory, Institute of Materials Structure Science, Tsukuba 305-0801, Japan3Institute of Applied Physics, University of Tsukuba, Tsukuba 305-8573, Japan
4
Faculty of Technology, Tokyo University of Agriculture and Technology, Tokyo 184-8588, JapanResults and Discussion

Figure 1 shows Mn L2,3 XMCD spectra taken at Τ = 200
K and 30 K at H = 5.0 T. The intensity has beennormalized to at the Mn L3 edge. The XMCD signal wasobserved even at 30 K, indicating that the MnP phase is
not a dominant component of the sample, because in MnPa ferromagnetic-to-anti-ferromagnetic transition occurs at
47 K. The XMCD spectra have two negative finestructures at the Mn L3. Structure A is dominant at 200 Kand structure B is dominant at 30 K. This difference may
be caused by a paramagnetic component in the sample.
Furthermore by applying the XMCD sum rules, Morb andMspin were obtained. Assuming that nd
5.0, Morb(200 K)~0.039 µB/Mn and Morb(30 K) ~0.159 µB/Mn. It appears
that at low temperature contributions from theparamagnetic component becomes large and that thesizable orbital magnetic moment appears.

H = 5.0 T
XMCD (arb. units)

Introduction
Recently the discovery of diluted magnetic
semiconductors (DMSs) which show room-temperature
ferromagnetism has been a hot issue. These materials arepromising candidates for spintronics devices. Some ofMn-doped II-IV-V2 (chalcopyrite) type DMSs show
room-temperature ferromagnetism, and attract muchattention. For instance, it is reported that TC’s ofZnGeP2:Mn and CdGeP2:Mn are ~350 K and ~320 K
respectively, well above room temperature [1, 2]. It isfound that Mn atoms substitute mainly for the II (Zn, Cd)sites in these materials. By ab initio calculations based on
local density approximation, the ferromagnetism derives
from the carriers which arise from the system withvacancies (II, Vc, Mn)GeP2 or non-stoichiometric (II, Ge,Mn)GeP2 [3]. In ZnGeP2:Mn, 100% Mn substitution i.e.
MnGeP2 was achieved [4].
In this work we have measured soft X-ray absorption(XAS), and soft X-ray magnetic circular dichroism(XMCD) spectra of MnGeP2 thin film to clarify theelectronic state and the origin of ferromagnetism of theMnGeP2 thin film by studying the magnetic state of theMn atoms.
Experimental
The MnGeP2 thin film was fabricated by the MBE
method. The thin film was deposited on a Ge buffer layeroat 435 C which was grown on a GaAs(001) substrate ato380 C. The Ge buffer layer enables a two-dimensional
growth of MnGeP2 thin film [5]. In order to eliminate
surface effects, the sample was capped with a 3nm Gelayer over the thin film. The fabricated MnGeP2 thin film
was transferred into a superconducting magnet under an-9ultra high vacuum of 10 Torr. The XAS and XMCD
spectra were taken in a total electron yield mode at 200 K
and 30 K with applied magnetic field at 5.0 T.
We have done a magnetization measurement for theMnGeP2 thin film in advance. The sample showed TC ~320
K and thus it was confirmed to be a room-temperature
ferromagnet. Additionally the M-T curve indicated that
there was a component which obeyed the Curie-Weiss law
in the sample. This fact suggested that a paramagnetic
component existed in the sample.

T = 200K

T = 30K

AB Mn L3637 638 639 640 641 642630640650660
Photon Energy (eV)Fig. 1: Mn L2,3 XMCD spectra of the MnGeP2 thin film
References[1] G. A. Medvedkin et al., J. Cryst Growth 236, 609(2002)[2] K. Sato et al., J. Appl. Phys. 89, 7027 (2001)[3] H. Akai et al., Phase Transitions 76, 401 (2003)[4] S. Cho et al., Solid State Commun. 129, 609 (2004)[5] K. Minami et al., Int. Conf. on Molecular Beam
Epitaxy, Edinburgh UK (2004)*osafune@wyvern.phys.s.u-tokyo.ac.jp

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