A method to measure the superconducting (SC) stiffness tensor Formula: see text, without subjecting the sample to external magnetic field, is applied to La
Sr
CuO
. The method is based on the London ...equation Formula: see text, where J is the current density and A is the vector potential which is applied in the SC state. Using rotor free A and measuring J via the magnetic moment of superconducting rings, Formula: see text at T → T
is extracted. The technique is sensitive to very small stiffnesses (penetration depths on the order of a few millimeters). The method is applied to two different rings: one with the current running only in the CuO
planes, and another where the current must cross planes. We find different transition temperatures for the two rings, namely, there is a temperature range with two-dimensional stiffness. Additional low energy muon spin rotation measurements on the same sample determine the stiffness anisotropy at T < T
.
Low Energy Measurements in Low-Energy µSR Suter, Andreas; Martins, Maria Mendes; Ni, Xiaojie ...
Journal of physics. Conference series,
03/2023, Letnik:
2462, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
In the context of
µ
SR studies on magnetic materials in the ordered state, often a strong initial depolarization is found in the zero field spectra. For transverse field measurements this is ...often referred to as a loss in asymmetry. In case of the low-energy
µ
SR (LE-
µ
SR) setup this needs a more detailed discussion since effects such as time-of-flight distribution of impinging muons, back scattering, and muon reflection will change the spectra at early times and low implantation energies
(E
< 3keV). These effects are well understood and reproducible allowing to correct for in any given experiment. We will discuss them and show how to correct for in experiments at low implantation energies.
Depth profiling of LE-µSR parameters with musrfit Martins, Maria Mendes; Suter, Andreas; Salman, Zaher ...
Journal of physics. Conference series,
03/2023, Letnik:
2462, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
The study of thin-film and multi-layered structures with nanometer resolution is possible with low energy
µ
SR (LE-
µ
SR). Modeling of the measured
µ
SR parameters such as diamagnetic ...asymmetry and relaxation rate as a function of sample depth can be obtained from a series of experimental implantation energy measurements and its correlation with the simulated stopping profiles. The fitting approach assumes a sharp transition between regions with distinct properties. The fitting method, previously developed in matlab, was implemented in musrfit, a free
µ
SR data analysis framework written in C++. The main goal is to make this fitting method widely available for energy dependent measurements and to increase the modeling possibilities within musrfit.
The organization of single-molecule magnets (SMMs) on surfaces via thermal sublimation is a prerequisite for the development of future devices for spintronics exploiting the richness of properties ...offered by these magnetic molecules. However, a change in the SMM properties due to the interaction with specific surfaces is usually observed. Here we present a rare example of an SMM system that can be thermally sublimated on gold surfaces while maintaining its intact chemical structure and magnetic properties. Muon spin relaxation and ac susceptibility measurements are used to demonstrate that, unlike other SMMs, the magnetic properties of this system in thin films are very similar to those in the bulk, throughout the full volume of the film, including regions near the metal and vacuum interfaces. These results exhibit the robustness of chemical and magnetic properties of this complex and provide important clues for the development of nanostructures based on SMMs.
Muonium is a hydrogen like bound system with a positive muon and an electron. Here the authors measure the Lamb shift and frequency of the transition from 2S1/2, F = 0 state to 2P1/2, F = 1 state in ...muonium atom and the hyperfine structure of the 2S level.
Two-dimensional magnetic systems with continuous spin degrees of freedom exhibit a rich spectrum of thermal behaviour due to the strong competition between fluctuations and correlations. When such ...systems incorporate coupling via the anisotropic dipolar interaction, a discrete symmetry emerges, which can be spontaneously broken leading to a low-temperature ordered phase. However, the experimental realisation of such two-dimensional spin systems in crystalline materials is difficult since the dipolar coupling is usually much weaker than the exchange interaction. Here we realise two-dimensional magnetostatically coupled XY spin systems with nanoscale thermally active magnetic discs placed on square lattices. Using low-energy muon-spin relaxation and soft X-ray scattering, we observe correlated dynamics at the critical temperature and the emergence of static long-range order at low temperatures, which is compatible with theoretical predictions for dipolar-coupled XY spin systems. Furthermore, by modifying the sample design, we demonstrate the possibility to tune the collective magnetic behaviour in thermally active artificial spin systems with continuous degrees of freedom.
Abstract
The interplay between spin-orbit interaction and magnetic order is one of the most active research fields in condensed matter physics and drives the search for materials with novel, and ...tunable, magnetic and spin properties. Here we report on a variety of unique and unexpected observations in thin multiferroic Ge
1−
x
Mn
x
Te films. The ferrimagnetic order parameter in this ferroelectric semiconductor is found to switch direction under magnetostochastic resonance with current pulses many orders of magnitude lower as for typical spin-orbit torque systems. Upon a switching event, the magnetic order spreads coherently and collectively over macroscopic distances through a correlated spin-glass state. Utilizing these observations, we apply a novel methodology to controllably harness this stochastic magnetization dynamics.
Iridates from the molecular side Pedersen, Kasper S; Bendix, Jesper; Tressaud, Alain ...
Nature communications,
07/2016, Letnik:
7, Številka:
1
Journal Article
Recenzirano
Odprti dostop
New exotic phenomena have recently been discovered in oxides of paramagnetic Ir(4+) ions, widely known as 'iridates'. Their remarkable properties originate from concerted effects of the crystal ...field, magnetic interactions and strong spin-orbit coupling, characteristic of 5d metal ions. Despite numerous experimental reports, the electronic structure of these materials is still challenging to elucidate, and not attainable in the isolated, but chemically inaccessible, IrO6(8-) species (the simplest molecular analogue of the elementary {IrO6}(8-) fragment present in all iridates). Here, we introduce an alternative approach to circumvent this problem by substituting the oxide ions in IrO6(8-) by isoelectronic fluorides to form the fluorido-iridate: IrF6(2-). This molecular species has the same electronic ground state as the {IrO6}(8-) fragment, and thus emerges as an ideal model for iridates. These results may open perspectives for using fluorido-iridates as building-blocks for electronic and magnetic quantum materials synthesized by soft chemistry routes.
Abstract
We have designed and constructed a thin film preparation chamber with base pressure of <2×10
−9
mbar. Currently, the chamber is equipped with two large area evaporators (a molecular ...evaporator and an electron-beam evaporator), an ion sputtering gun, a thickness monitor and a substrate heater. It is designed such that it can handle large area thin film samples with a future possibility to transfer them in vacuum directly to the low energy muons (LEM) spectrometer or to other advanced characterization facilities in the Quantum Matter and Materials Center (QMMC) which will be constructed in 2024. Initial commissioning of the chamber resulted in high quality, large area and uniform molecular films of CuPc and TbPc
2
on various substrate materials. We present first results from low energy
µ
SR (LE-
µ
SR) measurements on these films.
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