Issue |
Europhys. Lett.
Volume 73, Number 5, March 2006
|
|
---|---|---|
Page(s) | 772 - 778 | |
Section | Condensed matter: electronic structure, electrical, magnetic, and optical properties | |
DOI | https://doi.org/10.1209/epl/i2005-10465-7 | |
Published online | 27 January 2006 |
Observation of the spontaneous vortex phase
in the weakly ferromagnetic superconductor
:
A penetration depth study
1
Department of Physics, University of Illinois at Urbana-Champaign 1110 W. Green Street, Urbana IL 61801, USA
2
Los Alamos National Laboratory, MST-10 - Los Alamos, NM 87545, USA
3
National Creative Research Initiative Center for Superconductivity and Department of Physics, Pohang University of Science and Technology Pohang 790-784, Republic of Korea
4
National Institute for Materials Science - 1-2-1 Sengen Tsukuba, Ibaraki 305-0047, Japan
Received:
3
November
2005
Accepted:
13
January
2006
The coexistence of weak ferromagnetism and superconductivity in
suggests the possibility of a spontaneous vortex
phase (SVP) in which vortices appear in the absence of an external
field. We report evidence for the long-sought SVP from the in-plane
magnetic penetration depth
of high-quality
single crystals of
. In addition to expected
features at the Néel temperature
and weak
ferromagnetic onset at
,
rises
to a maximum at
before dropping sharply down to
. We assign the
maximum to the proliferation and
freezing of spontaneous vortices. A model proposed by Koshelev and
Vinokur explains the increasing
as a
consequence of increasing vortex density, and its subsequent
decrease below Tm as defect pinning suppresses vortex hopping.
PACS: 74.25.Nf – Response to electromagnetic fields (nuclear magnetic resonance, surface impedance, etc.) / 74.25.Ha – Magnetic properties / 74.70.Dd – Ternary, quaternary and multinary compounds (including Chevrel phases, borocarbides, etc.)
© EDP Sciences, 2006
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