23 research outputs found
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Role of topology in compensated magnetic systems
Topology plays a crucial and multifaceted role in solid state physics, leading to a remarkable array of newly investigated materials and phenomena. In this Perspective, we provide a brief summary of well-established model materials with a particular focus on compensated magnets and highlight key phenomena that emerge due to the influence of topology in these systems. The overview covers various magneto-transport phenomena, with a particular focus on the extensively investigated anomalous magneto-transport effects. Furthermore, we look into the significance of topology in understanding elementary magnetic excitations, namely magnons, where the role of topology gained considerable attention from both theoretical and experimental perspectives. Since electrons and magnons carry energy, we explore the implications of topology in combined heat and spin transport experiments in compensated magnetic systems. At the end of each section, we highlight intriguing unanswered questions in this research direction. To finally conclude, we offer our perspective on what could be the next advancements regarding the interaction between compensated magnetism and topology
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Magneto-thermal transport indicating enhanced Nernst response in FeCo/IrMn exchange coupled stacks
We present an analysis of magneto-thermal transport data in IrMn/FeCo bilayers based on the Mott relation and report an enhancement of the Nernst response in the vicinity of the blocking temperature. We measure all four transport coefficients of the longitudinal resistivity, anomalous Hall resistivity, Seebeck effect, and anomalous Nernst effect, and we show a deviation arising around the blocking temperature between the measured Nernst coefficient and the one calculated using the Mott rule. We attribute this discrepancy to spin fluctuations at the antiferromagnet/ferromagnet interface near the blocking temperature. The latter is estimated by magnetometry and magneto-transport measurements
Anomalous Nernst effect in perpendicularly magnetised {\tau}-MnAl thin films
-MnAl is interesting for spintronic applications as a ferromagnet with
perpendicular magnetic anisotropy due to its high uniaxial magnetocrystalline
anisotropy. Here we report on the anomalous Nernst effect of sputter deposited
-MnAl thin films. We demonstrate a robust anomalous Nernst effect at
temperatures of 200 K and 300 K with a hysteresis similar to the anomalous Hall
effect and the magnetisation of the material. The anomalous Nernst coefficient
of (0.60.24) V/K at 300 K is comparable to other perpendicular
magnetic anisotropy thin films. Therefore -MnAl is a promising candidate
for spin-caloritronic research
All Electrical Access to Topological Transport Features in MnPtSn Films
The presence of non-trivial magnetic topology can give rise to non-vanishing
scalar spin chirality and consequently a topological Hall or Nernst effect. In
turn, topological transport signals can serve as indicators for topological
spin structures. This is particularly important in thin films or nanopatterned
materials where the spin structure is not readily accessible. Conventionally,
the topological response is determined by combining magnetotransport data with
an independent magnetometry experiment. This approach is prone to introduce
measurement artifacts. In this study, we report the observation of large
topological Hall and Nernst effects in micropatterned thin films of
MnPtSn below the spin reorientation temperature K. The magnitude of the topological Hall effect
nm is close to the value reported in
bulk MnPtSn, and the topological Nernst effect nV K measured in the same microstructure has a similar magnitude as
reported for bulk MnGe ( nV K), the
only other material where a topological Nernst was reported. We use our data as
a model system to introduce a topological quantity, which allows to detect the
presence of topological transport effects without the need for independent
magnetometry data. Our approach thus enables the study of topological transport
also in nano-patterned materials without detrimental magnetization related
limitations.Comment: 8 pages, 3 figure
Anomalous Hall effect and magnetoresistance in micro-ribbons of the magnetic Weyl semimetal candidate PrRhC2
PrRhC2 belongs to the rare-earth carbides family whose properties are of
special interest among topological semimetals due to the simultaneous breaking
of both inversion and time-reversal symmetry. The concomitant absence of both
symmetries grants the possibility to tune the Weyl nodes chirality and to
enhance topological effects like the chiral anomaly. In this work, we report on
the synthesis and compare the magnetotransport measurements of a poly- and
single crystalline PrRhC2 sample. Using a remarkable and sophisticated
technique, the PrRhC2 single crystal is prepared via focused ion beam cutting
from the polycrystalline material. Our magnetometric and specific heat analyses
reveal a non-collinear antiferromagnetic state below 20K, as well as
short-range magnetic correlations and/or magnetic fluctuations well above the
onset of the magnetic transition. The transport measurements on the PrRhC2
single crystal display an electrical resistivity peak at 3K and an anomalous
Hall effect below 6K indicative of a net magnetization component in the ordered
state. Furthermore, we study the angular variation of magnetoresistivities as a
function of the angle between the in-plane magnetic field and the injected
electrical current. We find that both the transverse and the longitudinal
resistivities exhibit fourfold angular dependencies due to higher-order terms
in the resistivity tensor, consistent with the orthorhombic crystal symmetry of
PrRhC2. Our experimental results may be interpreted as features of topological
Weyl semimetallic behavior in the magnetotransport properties
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Imaging and writing magnetic domains in the non-collinear antiferromagnet Mn3Sn
Non-collinear antiferromagnets are revealing many unexpected phenomena and they became crucial for the field of antiferromagnetic spintronics. To visualize and prepare a well-defined domain structure is of key importance. The spatial magnetic contrast, however, remains extraordinarily difficult to be observed experimentally. Here, we demonstrate a magnetic imaging technique based on a laser induced local thermal gradient combined with detection of the anomalous Nernst effect. We employ this method in one the most actively studied representatives of this class of materials—Mn3Sn. We demonstrate that the observed contrast is of magnetic origin. We further show an algorithm to prepare a well-defined domain pattern at room temperature based on heat assisted recording principle. Our study opens up a prospect to study spintronics phenomena in non-collinear antiferromagnets with spatial resolution
Saturation of the anomalous Hall effect at high magnetic fields in altermagnetic RuO2
Observations of the anomalous Hall effect in RuO and MnTe have
demonstrated unconventional time-reversal symmetry breaking in the electronic
structure of a recently identified new class of compensated collinear magnets,
dubbed altermagnets. While in MnTe the unconventional anomalous Hall signal
accompanied by a vanishing magnetization is observable at remanence, the
anomalous Hall effect in RuO is excluded by symmetry for the N\'eel vector
pointing along the zero-field [001] easy-axis. Guided by a symmetry analysis
and ab initio calculations, a field-induced reorientation of the N\'eel vector
from the easy-axis towards the [110] hard-axis was used to demonstrate the
anomalous Hall signal in this altermagnet. We confirm the existence of an
anomalous Hall effect in our RuO thin-film samples whose set of magnetic
and magneto-transport characteristics is consistent with the earlier report. By
performing our measurements at extreme magnetic fields up to 68 T, we reach
saturation of the anomalous Hall signal at a field 55 T that
was inaccessible in earlier studies, but is consistent with the expected
N\'eel-vector reorientation field.Comment: 4 figure
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Saturation of the anomalous Hall effect at high magnetic fields in altermagnetic RuO2
Observations of the anomalous Hall effect in RuO2 and MnTe have demonstrated unconventional time-reversal symmetry breaking in the electronic structure of a recently identified new class of compensated collinear magnets, dubbed altermagnets. While in MnTe, the unconventional anomalous Hall signal accompanied by a vanishing magnetization is observable at remanence, the anomalous Hall effect in RuO2 is excluded by symmetry for the Néel vector pointing along the zero-field [001] easy-axis. Guided by a symmetry analysis and ab initio calculations, a field-induced reorientation of the Néel vector from the easy-axis toward the [110] hard-axis was used to demonstrate the anomalous Hall signal in this altermagnet. We confirm the existence of an anomalous Hall effect in our RuO2 thin-film samples, whose set of magnetic and magneto-transport characteristics is consistent with the earlier report. By performing our measurements at extreme magnetic fields up to 68 T, we reach saturation of the anomalous Hall signal at a field Hc ≃ 55 T that was inaccessible in earlier studies but is consistent with the expected Néel-vector reorientation field