排序方式: 共有25条查询结果,搜索用时 31 毫秒
1.
E. Morenzoni E. M. Forgan H. Glückler T. J. Jackson H. Luetkens Ch. Niedermayer T. Prokscha T.M. Riseman M. Birke A. Hofer J. Litterst M. Pleines G. Schatz 《Hyperfine Interactions》2001,133(1-4):179-195
The recent development at the Paul Scherrer Institute of a beam of low energy muons allows depth dependent muon spin rotation and relaxation investigations in thin samples, multilayers and near surface regions (low energy SR, LE-SR). After a brief overview of the LE-SR method, some representative experiments performed with this technique will be presented. The first direct determination of the field profile just below the surface of a high-temperature superconductor in the Meissner phase illustrates the power and sensitivity of low energy muons as near-surface probe and is an example of general application to depth profiling of magnetic fields. The evolution of the flux line lattice distribution across the surface of a YBa2Cu3O7 film in the vortex phase has been investigated by implanting muons on both sides of a normal-superconducting boundary. A determination of the relaxation time and energy barrier to thermal activation in iron nanoclusters, embedded in a silver thin film matrix (500nm), demonstrates the use of slow muons to measure the properties of samples that cannot be made thick enough for the use of conventional SR. Other experiments investigated the magnetic properties of thin Cr(001) layers at thicknesses above and below the collapse of the spin density wave. 相似文献
2.
Prokscha T Morenzoni E Eshchenko DG Garifianov N Glückler H Khasanov R Luetkens H Suter A 《Physical review letters》2007,98(22):227401
The formation of hydrogenlike muonium (Mu) has been studied as a function of implantation energy in intrinsic Si, thin films of condensed van der Waals gases (N2, Ne, Ar, Xe), fused and crystalline quartz, and sapphire. By varying the initial energy of positive muons (mu+) between 1 and 30 keV the number of electron-hole pairs generated in the ionization track of the mu+ can be tuned between a few and several thousand. The results show the strong suppression of the formation of those Mu states that depend on the availability of excess electrons. This indicates that the role of H-impurity states in determining electric properties of semiconductors and insulators depends on the way in which atomic H is introduced into the material. 相似文献
3.
Morenzoni E Luetkens H Prokscha T Suter A Vongtragool S Galli F Hesselberth MB Garifianov N Khasanov R 《Physical review letters》2008,100(14):147205
We have performed depth dependent muon-spin-rotation and -relaxation studies of the dynamics of single layer films of AuFe and CuMn spin glasses as a function of thickness and of its behavior as a function of distance from the vacuum interface (5-70 nm). A significant reduction in the muon-spin relaxation rate as a function of temperature with respect to the bulk material is observed when the muons are stopped near (5-10 nm) the surface of the sample. A similar reduction is observed for the whole sample if the thickness is reduced to, e.g., 20 nm and less. This reflects an increased impurity spin dynamics (incomplete freezing) close to the surface although the freezing temperature is only modestly affected by the dimensional reduction. 相似文献
4.
Klauss H.-H. Baabe D. Mienert D. Birke M. Luetkens H. Litterst F. J. Hücker M. Büchner B. Cheong S. W. 《Hyperfine Interactions》2001,136(3-8):711-715
We report zero field μSR experiments on the lanthanum nickelate La2−x
Sr
x
NiO4+δ system with strontium doping level x between 0 and 0.6. In a single crystal with x=0.33 the internal field distribution shows two separated signals reflecting the antiferromagnetic domains and the non magnetic
antiphase domain walls in the spin and charge ordered state below 190 K. Below 70 K a broadening of the low field line is
observed. A similar behavior is observed in polycrystalline samples with 0.2≤x≤0.5.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
5.
6.
Wiesenmayer E Luetkens H Pascua G Khasanov R Amato A Potts H Banusch B Klauss HH Johrendt D 《Physical review letters》2011,107(23):237001
It is widely believed that, in contrast to its electron-doped counterparts, the hole-doped compound Ba(1-x)K(x)Fe(2)As(2) exhibits a mesoscopic phase separation of magnetism and superconductivity in the underdoped region of the phase diagram. Here, we report a combined high-resolution x-ray powder diffraction and volume-sensitive muon spin rotation study of Ba(1-x)K(x)Fe(2)As(2) showing that this paradigm does not hold true in the underdoped region of the phase diagram (0≤x≤0.25). Instead we find a microscopic coexistence of the two forms of order. A competition of magnetism and superconductivity is evident from a significant reduction of the magnetic moment and a concomitant decrease of the magnetoelastically coupled orthorhombic lattice distortion below the superconducting phase transition. 相似文献
7.
A. Amato R. Khasanov H. Luetkens H.-H. Klauss 《Physica C: Superconductivity and its Applications》2009,469(9-12):606-613
In this short review, we attempt to give a comprehensive discussion of studies performed to date by muon-spin spectroscopy (more precisely the relaxation and rotation technique, also know as μSR) on the recently discovered layered iron-based superconductors. On one side, μSR has been used to characterize the magnetic state of different families of layered iron-based systems. Similarly the subtle interplay of the magnetic state and the structural transition present in some families has been investigated. We will also discuss the information provided by this technique on the interaction between the magnetic state and the superconducting phase. Finally the μSR technique has been used to investigate the magnetic penetration depth of the superconducting ground state. The study of its absolute value, temperature and magnetic field dependence provides crucial tests for investigating possible unconventional superconducting states in such systems. 相似文献
8.
Roland Hord Gerhard Cordier Kathrin Hofmann Alexander Buckow Gwendolyne Pascua Hubertus Luetkens Prof. Dr. Lambert Alff Prof. Dr. Barbara Albert 《无机化学与普通化学杂志》2011,637(9):1114-1117
Through low‐temperature synthesis in CsOH flux, lanthanum cuprate La2CuO4 can be obtained in a metastable form, the so‐called T′ modification (tetragonal, I4/mmm, no. 139, a = 400.95(2) pm, c = 1254.08(7) pm). When heated, this T′ phase transforms into a K2NiF4‐type modification, whose crystal structure was now refined from X‐ray powder data (tetragonal, I4/mmm, no. 139, a = 383.29(3) pm, c = 1331.3(2) pm at T = 1073 K). The well‐known orthorhombic phase (s.g. Cmce, no. 64, a = 536.14(3) pm, b = 1315.53(8) pm, c = 540.20(3) pm) – usually obtained via conventional solid state synthesis – was observed to form upon cooling from the K2NiF4‐type modification. High‐temperature powder diffractometry allowed crystal structure refinements for all of the three phases. 相似文献
9.
Luetkens H Klauss HH Khasanov R Amato A Klingeler R Hellmann I Leps N Kondrat A Hess C Köhler A Behr G Werner J Büchner B 《Physical review letters》2008,101(9):097009
We present zero field and transverse field muon spin relaxation experiments on the recently discovered Fe-based superconductor LaFeAsO1-xFx (x=0.075 and x=0.1). The temperature dependence of the deduced superfluid density is consistent with a BCS s-wave or a dirty d-wave gap function, while the field dependence strongly evidences unconventional superconductivity. We obtain the in-plane penetration depth of lambda ab(0)=254(2) nm for x=0.1 and lambda ab(0)=364(8) nm for x=0.075. Further evidence for unconventional superconductivity is provided by the ratio of Tc versus the superfluid density, which is close to the Uemura line of high-Tc cuprates. 相似文献
10.
Luetkens H Stingaciu M Pashkevich YG Conder K Pomjakushina E Gusev AA Lamonova KV Lemmens P Klauss HH 《Physical review letters》2008,101(1):017601
We report muon-spin relaxation measurements on the magnetic structures of RBaCo2O(5.5) with R=Y, Tb, Dy, and Ho. Three different phases, one ferrimagnetic and two antiferromagnetic, are identified below 300 K. They consist of different ordered spin state arrangements of high-, intermediate-, and low-spin Co3+ of CoO6 octahedra. Phase separation into well separated regions with different spin state order is observed in the antiferromagnetic phases. The unusual strongly anisotropic magnetoresistance and its onset at the FM-AFM phase boundary is explained. 相似文献