Searcharxiv⌕ Search

arXiv subjects

J. Spring

Publications and source records attributed to J. Spring.

5 recordsLinked to original sources

Strain-Induced Metal-to-Insulator Transition in Antiferromagnetic SrCrO$_3$ Thin Films

Antiferromagnetic (AF) metals are rare, yet they combine properties attractive for spintronic devices like robustness against stray fields and electrical readout. Among AF metal oxide candidates, SrCrO$_3$ remains largely unexplored due to its notoriously difficult synthesis. In this paper, we demonstrate the growth of high-quality SrCrO$_3$ thin films by magnetron sputtering on substrates that impose a wide range of tensile and compressive strains. Muon spin relaxation experiments, supported by x-ray magnetic dichroism, unveil the emergence of an AF phase with dilute magnetic disorder at low temperatures, while resistivity measurements confirm the simultaneous metallic ground state of SrCrO$_3$ under low strain. As both compressive and tensile strain increase, a metal-to-insulator transition is induced in the films, while the onset of the magnetic transition temperature remains unchanged. Moreover, an intriguing resistivity upturn, accompanied by a change in the dominant charge-carrier type, occurs at a temperature that correlates with strain. These observations suggest a complex strain-dependent band structure, with strain-induced Jahn-Teller distortions or tilting of the CrO$_6$ octahedra that emerge depending on the sign of the strain, as inferred from density functional theory calculations.

cond-mat.mtrl-sci↗

Microscopic study of the impurity effect in the kagome superconductor La(Ru$_{1-x}$Fe$_{x}$)$_{3}$Si$_{2}$

We report on the effect of magnetic impurities on the microscopic superconducting (SC) properties of the kagome-lattice superconductor La(Ru$_{1-x}$Fe$_{x}$)$_{3}$Si$_{2}$ using muon spin relaxation/rotation. A strong suppression of the superconducting critical temperature $T_{\rm c}$, the SC volume fraction, and the superfluid density was observed. We further find a correlation between the superfluid density and $T_{\rm c}$ which is considered a hallmark feature of unconventional superconductivity. Most remarkably, measurements of the temperature-dependent magnetic penetration depth $λ$ reveal a change in the low-temperature behavior from exponential saturation to a linear increase, which indicates that Fe doping introduces nodes in the superconducting gap structure at concentrations as low as $x=$~0.015. Our results point to a rare example of unconventional superconductivity in the correlated kagome lattice and accessible tunability of the superconducting gap structure, offering new insights into the microscopic mechanisms involved in superconducting order.

cond-mat.supr-con↗

Local spectroscopic evidence for a nodeless magnetic kagome superconductor CeRu$_2$

We report muon spin rotation ($μ$SR) experiments on the microscopic properties of superconductivity and magnetism in the kagome superconductor CeRu$_{2}$ with $T_{\rm c}$~${\simeq}$~5~K. From the measurements of the temperature-dependent magnetic penetration depth $λ$, the superconducting order parameter exhibits nodeless pairing, which fits best to an anisotropic $s$-wave gap symmetry. We further show that the $T_{\rm c}$/$λ^{-2}$ ratio is comparable to that of unconventional superconductors. Furthermore, the powerful combination of zero-field (ZF)-$μ$SR and high-field $μ$SR has been used to uncover magnetic responses across three characteristic temperatures, identified as $T_1^*$~${\simeq}$~110~K, $T_2^*$~${\simeq}$~65~K, and $T_3^*$~${\simeq}$~40~K. Our experiments classify CeRu$_{2}$ as an exceedingly rare nodeless magnetic kagome superconductor.

cond-mat.supr-con↗

Robust ferromagnetism in insulating La$_2$NiMnO$_6$ thin films

The field of oxide spintronics can strongly benefit from the establishment of robust ferromagnetic insulators with near room-temperature Curie temperature. Here we investigate the structural, electronic, and magnetic properties of atomically-precise epitaxially-strained thin films of the double perovskite La$_2$NiMnO$_6$ (LNMO) grown by off-axis radio-frequency magnetron sputtering. We find that the films retain both a strong insulating behavior and a bulk-like Curie temperature in the order of 280 K, nearly independently from epitaxial strain conditions. These results suggest a prospective implementation of LNMO films in multi-layer device architectures where a high-temperature ferromagnetic insulating state is a prerequisite.

cond-mat.mtrl-sci↗

The Advanced Light Source Accelerator Control System at Ten Years from Commissioning

The Advanced Light Source was commissioned 10 years ago using the newly constructed control system. Further experience with the control system was reported in 1993. In this publication, we report on recent experience with the operation and especially growth of the computer control system and expansion to accommodate the new superconducting bend magnets and fast orbit feedback for the ALS electron storage ring.

physics.acc-ph↗