Low Energy Muon Spin Relaxation of T’ cuprate superconductors
K.M. Kojima1,2 , M. Hiraishi2 , M. Miyazaki2 , A. Koda1,2 , R. Kadono1,2 , A. Suter3 , H.
Luetkens3 , Z. Salman3 , T. Prokscha3 , E. Morenzoni3 , Y. Krockenberger4 , H. Yamamoto4 ,A. Ikeda5 and M. Naito5
1We have performed low-energy muon spin relaxation (LE-µSR) measurement of MOD-grown
Eu2 CuO4 (80nm thickness) and MBE-grown(La,Y)2 CuO4 (300nm thickness), both of whichtakes the T 0 -structure. After careful annealing
to remove excess oxygens, the thin-film samples
exhibit superconducting transitions at Tc = 21K(LYCO) and Tc = 26K (ECO) without cation substitution for doping [2,3]. Our LE-µSR has detected magnetic muon spin relaxation with a partial (∼ 1/5 − 1/3) magnetic volume fraction in thesuperconducting samples. The magnetic volume
fraction of as-grown ECO (non-SC) is significantly
larger and the magnetic ordering temperature issignificantly higher than those for the annealed
ECO (Tc =26K), exhibiting the anti-correlation between the static magnetism and the superconductivity, as has been reported previously in many(bulk) cuprate superconductors coexisting withmagnetism (Fig.1).
In MBE-grown LYCO, the magnetic volume fraction is larger near the surface than in the deep region. In the same sample, we were able to measure
the Meissner shielding profile of the applied mag-)*.

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Low energy muon beam, which has an energy ofa few to mid-twenty keV makes it possible to stopmuons into thin-film samples with the thickness of∼100 nm. Utilizing the muon spin relaxation (µSR)
technique, low energy muon beam provides a uniquemagnetic probe of thin-film samples [1], including
the molecular beam epitaxy (MBE)-grown or metalorganic decomposition (MOD)-grown superconductor thin-films. At the moment, low energy muon
beam is available only at Paul Sherrer Institute(PSI), Switzerland, utilizing a cryogenic gas moderation to energetic (∼4MeV) muons generated via
nuclear reactions [1]. The low-energy muons at PSI
may be stopped at 100nm depth with the spreadof the depth+20/−30nm at the half maximum of
the stopping profile. Eventhough the depth resolution is not very sharp, it provides a unique opportunity to scan the magnetic volume fractions andthe Meissner shielding of the applied magnetic field
as a function of the depth within the thin-film.

0!1%%&#21Muon Science Laboratory, Institute of Materials Structure Science, KEK and Material and Life Science
Experimental Facility, J-PARC, Tokai, 319-1195, Japan
2
SOKENDAI, Tsukuba, 305-0801, Japan
3
Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
4
NTT Basic Research Laboratories, Atsugi, 243-0198, Japan
5
Department of Applied Physics, Tokyo University of Agliculture and Technology, Koganei, 184-8588,
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Fig. 1: Zero-field muon spin relaxation spectra at 5K
with the inplantation energy of E = 4keV (upper) andthe non-magnetic volume fraction as a function of temperature (lower) for T’-Eu2 CuO4 MOD film: reduced(Tc = 26K) and as-grown (non-SC) samples.

netic field. This indicates a bulk superconductivityof non-doped T’ cuprate. Our preliminary analysis
suggests an elongated magnetic penetration depthof superconductivity (λ) near the surface than in
the center of the thin-film. This also suggests thecompeting feature of static magnetism and the superconductivity within the thin-film sample.
[1]E. Morenzoni, Physica B 404, 577, (2009) and references therein.
[2] O. Matsumoto et al., Phys. Rev. B 79, Art. No.
100508(R), (2009).
[3] A. Tsukada et al., Physica C 426-431, 459, (2005);
Solid State Commun. 133, 427, (2005).