Photon Factory Activity Report 2014 #32 (2015) B

BL-2A/BL-2 立ち上げ調整Soft X-ray Angle Resolved Photoemission Study of the Diluted MagneticSemiconductor Ba1-xKx(Zn1-yMny)2As2 Single Crystals
Hakuto Suzuki1,*, Guoqiang Zhao2, Kan Zhao2, Bijuan Chen2, Masafumi Horio1, Keisuke Koshiishi1,Jian Xu1, Masaki Kobayashi3, Makoto Minohara3, Enju Sakai3, Koji Horiba3, Hiroshi Kumigashira3,
Bo Gu4, Sadamichi Maekawa4, Yasutomo J. Uemura5, Changqin Jin2 and Atsushi Fujimori1
1
University of Tokyo, Tokyo 113-0033, Japan2
Chinese Academy of Sciences, Beijing 100190, China
3
KEK, Photon Factory, Tsukuba, 305-0801, Japan
4
Japan Atomic Energy Agency, Tokai 319-1195, Japan
5
Columbia University, New York 10027, USA
1 Introduction
Diluted magnetic semiconductors (DMSs) have attracted
considerable attention as a candidate for future
spintronics devices after the discovery of ferromagnetismin Mn-doped GaAs (GaMnAs). A new series of DMS,
Ba1-xKx(Zn1-yMny)2As2(Mn-BaZn2As2),
whichisisostructural to the ``122''-type iron-based hightemperature
superconductors,
wassuccessfullysynthesized recently with the TC as high as 230 K [1].
This material has an advantage that the Ba layer, wherehole carriers are introduced, and the ZnAs layer, wheremagnetic elements are, are spatially separated. This
property allows us to independently control the amount ofcarriers and that of magnetic element. Also, the equal
chemical valence 2+ of the magnetic element Mn and thehost Zn atoms does not cause low chemical solubility
problem always present in GaMnAs and related DMSs,
which makes it possible to obtain bulk specimens.
Furthermore, interstitial sites for Mn ions in the ZnAs
layers are energetically unstable and thus the Mn ionstakes only substitutional ones, which significantly
simplifies the theoretical treatment and experimental
understanding of the carrier-induced ferromagnetism inthis material.

spectra taken with hν = 720 and 680 eV photons. The kz
positions approximately correspond to those of the Γ andZ point, respectively. The corresponding second
derivative plots along the energy directions are also
shown in Figs. 1 (c) and (d). Around the Γ point, weobserve that two hole bands cross EF, while around the Zpoint one hole and an electron band cross EF. The
appearance of multiple hole FSs and small electron
pocket around the Z point in the hole-doped MnBaZn2As2 is consistent with the calculated band structureof the host semiconductor BaZn2As2 [2].
ΓΓ

Γ

Γ

2 Experiment
In the present work, we have performed x-ray absorption
spectroscopy (XAS) and angle-resolved photoemission
spectroscopy (ARPES) measurements on Mn-BaZn2As2(x=0.3, y=0.15, TC = 60 K) single crystals. The newly
developed Beamline 2A is equipped with two undulatorsfor vacuum ultraviolet (VUV) and soft x-ray (SX) light,
respectively, enabling us to measure samples with a wide
range of photons (from ~20 eV to ~1500 eV) at the same
sample position.

Fig. 1: (a), (b) Valence-band soft x-ray angle-resolved
photoemission spectroscopy intensity plots taken with hν= 720 and 680 eV photons. The kz positions correspond toΓ and Z point, respectively. (c), (d) Corresponding second
derivative plots.

3 Results and Discussion
The SX light increases the photoemission cross section
from the As 4p orbitals and the increased probing depth
provides us with information about the bulk low-energy
electronic structure. Figs. 1 (a) and (b) show ARPES

References[1] K. Zhao_et al., Nat. Commun. 4, 1442 (2013).
[2] H. Suzuki et al., Phys. Rev. B 91, 140401(R) (2015)* hakuto@wyvern.phys.s.u-tokyo.ac.jp

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