Deutsche Tagung f ¨ur Forschung mit ... - SNI-Portal

Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P56
Depth dependent studies of magnetic and superconducting properties with
polarized low energy muons
Elvezio Morenzoni 1 , Thomas Prokscha 1 , Andreas Suter 1 , Hubertus
Luetkens 1,2 , Dimitry Eshchenko 1,3 , Ted Forgan 4 , Hugo Keller 3 , Jochen
Litterst 2 , Günter Schatz 5 , Gerard Nieuwenhuys 6
1 Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, Villigen, Switzerland
– 2 IMNF, TU Braunschweig, Braunschweig, Germany – 3 Physik Institut, U. Zürich,
Zürich, Switzerland – 4 School of Physics and Astronomy, U. of Birmingham, Birmingham,
U.K. – 5 Fakultät für Physik, U. Konstanz, Konstanz, Germany – 6 Kamerling
Onnes Laboratory, Leiden U., Leiden, The Netherlands
Positive muons with 100 % spin polarization and whose energy can be continuously
varied from 0.5 to 30 keV represent a novel extension of the µSR technique allowing
depth dependent µSR-studies of thin films and multilayered structures in the range
from ∼ 1 nm to ∼ 200 nm [1]. They act as a non-destructive microscopic probe for
local investigations and provide unique information about magnetic and superconducting
properties. A new beam line, specially designed to maximize the low energy muon
flux, and an upgraded apparatus for µSR spectroscopy have been recently built and
commissioned at PSI [2]. It has been supported by contributions of BMBF, EPSCR
and various universities. The new set-up provides an intensity increase by almost a
factor of ten with respect to the past and will contribute to the realization of the full
potential offered by the use of polarized positive muons as nanoprobes. In this talk
we will give an introduction of the method and present some experiments recently performed.
Experiments include depth dependent studies of thin films, single layers and
heterostructures of magnetic and superconducting materials. Specifically, the measurement
of the value of the local magnetic field as a function of position below a surface on
a scale of a few nm has been used to map non-conventional and conventional superconductors
in the Meissner and vortex state, to study oxygen isotope effects on the magnetic
penetration depth, or to quantify non-local effects in superconductors [3,4,5]. In
multilayered structures (ferromagnetic/nonmagnetic/ferromagnetic) low energy muons
probe the oscillating conduction electron spin polarization responsible for the interlayer
exchange coupling [6] and in thin ferromagnetic/superconducting/ferromagnetic hybrid
structures they are used to characterize coexistence and coupling of a spin density wave
with bulk superconductivity [7].
[1] E. Morenzoni et al., Phys. Rev. Lett., 72, 2793 (1994)
[2] T. Prokscha et al., Physica B 374-375, 460-464 (2006)
[3] T. Jackson et al., Phys. Rev. Lett., 84, 4958 (2000)
[4] A. Suter et al., Phys. Rev. Lett. 92, 087001 (2004)
[5] R. Khasanov et al., Phys. Rev. Lett. 92, 057602 (2004)
[6] H. Luetkens et al., Phys. Rev. Lett. 91, 017204 (2003)
[7] A. Drew et al., Phys. Rev. Lett. 95, 197201 (2005)