Bipartite magnetic parent phases in the iron oxypnictide
superconductor
M. Hiraishi1, S. Iimura2, K. M. Kojima1,3*, J. Yamaura4, H. Hiraka1, K. Ikeda1,P. Miao1,3, Y. Ishikawa1, S. Torii1, M. Miyazaki1, I. Yamauchi1, A. Koda1,3, K. Ishii5,
M. Yoshida5,6, J. Mizuki6, R. Kadono1,3, R. Kumai1,3, T. Kamiyama1,3, T. Otomo1,3,Y. Murakami1,3, S. Matsuishi4 and H. Hosono2,41Institute of Materials Structure Science, High Energy Accelerator Research Organization(KEK), and Materials and Life-science experimental Facility J-PARC, Ibaraki, Japan,
2Materials and Structures Laboratory, Tokyo Institute of Technology, Kanagawa, Japan,
3
Department of Materials Structure Science, The Graduate University for Advanced Studies,Ibaraki, Japan,
4
Materials Research Center for Element Strategy, Tokyo Institute of Technology, Kanagawa,Japan,
5
SPring-8, Japan Atomic Energy Agency, Hyogo, Japan,
6
School of Science and Technology, Kwansei Gakuin University, Hyogo, Japan.

Temperature (K)* corresponding author: E-mail kenji.kojima@kek.jp
Iron oxypnictide is a new class of high-Tc superconductors which have iron instead of copperas the ingredient. We have employed coherently the two experimental probes (muon andneutron) available at MLF, J-PARC and additionally synchrotron X-ray available at Photon
Factroy, KEK to report the discovery of an antiferromagnetic phase as well as a uniquestructural transition in electron-overdoped LaFeAsO1−xHx [1]. A second parent phase isuncovered, albeit heavily doped (x ∼ 0.5). The unprecedented two-dome superconducting
phases observed in this material can be interpreted
asPHYSICS
a consequenceof the carrier doping
NATURE
DOI: 10.1038/NPHYS2906
starting from the original x ∼ 0 and additional xTN∼ 0.5 parent phases towards the intermediate
ImI ∼ 1.21 µB
ImI ∼ 0.63 µB
150
TsTs’region (x ∼ 0.2). The bipartite parent phases
FeTcwith distinct physical properties in the second
100
magnetic phase provide us with an interesting
AF1FeFe
example to illustrate the intimate interplay
AsAs
AF250
between the magnetic interaction, structural
SC2
SC1change and orbital degree of freedom in ironpnictide superconductors.
00.1
0.2
0.3
0.0
0.4
0.5
References
Hydrogen content x[1] M. Hiraishi et al. Nat. Phys. 10, 300
Fig.1:
Magneticand structuralphase
Figure 4| Magnetic,
structural and superconducting
phase diagramofdiagram
of
LaFeAsO
HCitefrom[1].
LaFeAsO
H.
The
original
parentcompoundwithx=0exhibits
a1 x x1−x x(2014).

structural transition at Ts = 155 K, followed by an antiferromagnetic state(AF1) at TN = 137 K (ref. 18). With increasing x, two superconductivity
domes appear: 0.05  x  0.20 (SC1) with Tc,max = 26 K, and0.20  x  0.42 (SC2) with Tc,max = 36 K (ref. 7). Eventually, another
antiferromagnetic phase (AF2) appears in the range 0.40  x  0.51. In theadvanced parent compound at x = 0.51, structural and magnetic transitions
occur at Ts ⇠ 95 K and TN = 89 K, respectively. Ts ’ indicates the c axis
upturn temperature observed in X-ray measurements. The filled and open

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