28 research outputs found
A hidden constant in the anomalous Hall effect of a high-purity magnet MnSi
Measurements of the Hall conductivity in MnSi can provide incisive tests of
theories of the anomalous Hall (AH) effect, because both the mean-free-path and
magnetoresistance (MR) are unusually large for a ferromagnet. The large MR
provides an accurate way to separate the AH conductivity from
the ordinary Hall conductivity . Below the Curie temperature
, is linearly proportional to (magnetization) with a
proportionality constant that is independent of both and . In
particular, remains a constant while changes by a factor
of 100 between 5 K and . We discuss implications of the hidden constancy
in .Comment: 5 pages, 4 figures. Minor change
Complex Antiferromagnetic Order in the Metallic Triangular Lattice Compound SmAuAlGe
The compounds AuAlGe ( lanthanide) form in a structure
that features two-dimensional triangular lattices of ions that are stacked
along the crystalline axis. Together with crystal electric field effects,
magnetic anisotropy, and electron-mediated spin exchange interactions, this
sets the stage for the emergence of strongly correlated spin and electron
phenomena. Here we investigate SmAuAlGe, which exhibits weak
paramagnetism that strongly deviates from conventional Curie-Weiss behavior.
Complex antiferromagnetic ordering emerges at 13.2 K and
7.4 K, where heat capacity measurements show that these
transitions are first and second order, respectively. These measurements also
reveal that the Sommerfeld coefficient is not enhanced compared to the
nonmagnetic analog YAuAlGe, consistent with the charge carrier
quasiparticles exhibiting typical Fermi liquid behavior. The
temperature-dependent electrical resistivity follows standard metallic
behavior, but linear magnetoresistance unexpectedly appears within the ordered
state. We compare these results to other AuAlGe materials, which
have already been established as localized -electron magnets that are hosts
for interesting magnetic and electronic phases. From this, SmAuAlGe
emerges as a complex quantum spin metal, inviting further investigations into
its properties and the broader family of related materials.Comment: 9 pages, 6 figure
Field-Induced Magnetic States in the Metallic Rare-Earth Layered Triangular Antiferromagnet TbAuAlGe
Magnetic frustration in metallic rare earth lanthanides () with
-electrons is crucial for producing interesting magnetic phases with high
magnetic anisotropy where intertwined charge and spin degrees of freedom lead
to novel phenomena. Here we report on the magnetic, thermodynamic, and
electrical transport properties of TbAuAlGe. Tb ions form 2-dimensional
triangular lattice layers which stack along the crystalline -axis. The
magnetic phase diagram reveals multiple nearly degenerate ordered states upon
applying field along the magnetically easy -plane before saturation. The
magnetoresistance in this configuration exhibits intricate field dependence
that closely follows that of the magnetization while the specific heat reveals
a region of highly enhanced entropy, suggesting the possibility of a
non-trivial spin textured phase. For fields applied along the -axis (hard
axis), we find linear magnetoresistance over a wide range of fields. We compare
the magnetic properties and magnetoresistance with an isostructral
GdAuAlGe single crystals. These results identify TbAuAlGe as an
environment for complex quantum spin states and pave the way for further
investigations of the broader AuAlGe family of materials.Comment: 8 pages, 5 figure
Non-saturating large magnetoresistance in semimetals
The rapidly expanding class of quantum materials known as {\emph{topological
semimetals}} (TSM) display unique transport properties, including a striking
dependence of resistivity on applied magnetic field, that are of great interest
for both scientific and technological reasons. However, experimental signatures
that can identify or discern the dominant mechanism and connect to available
theories are scarce. Here we present the magnetic susceptibility (), the
tangent of the Hall angle () along with magnetoresistance in four
different non-magnetic semimetals with high mobilities, NbP, TaP, NbSb and
TaSb, all of which exhibit non-saturating large MR. We find that the
distinctly different temperature dependences, and the values of
in phosphides and antimonates serve as empirical criteria to
sort the MR from different origins: NbP and TaP being uncompensated semimetals
with linear dispersion, in which the non-saturating magnetoresistance arises
due to guiding center motion, while NbSb and TaSb being {\it
compensated} semimetals, with a magnetoresistance emerging from nearly perfect
charge compensation of two quadratic bands. Our results illustrate how a
combination of magnetotransport and susceptibility measurements may be used to
categorize the increasingly ubiquitous non-saturating large magnetoresistance
in TSMs.Comment: Accepted for publication at Proc. Natl. Acad. Sci., minor revisions,
6 figure
Generic magnetic field dependence of thermal conductivity in magnetic insulators via hybridization of acoustic phonons and spin-flip excitations
Magnetic insulators provide excellent playgrounds to realize a range of
exciting spin models, some of which predict exotic spin ground states, and
thermal transport properties have been taking center stage in probing the spin
excitations. Despite the fact that acoustic phonons make the major contribution
to heat conduction in a crystalline system, their interplay with magnetic
excitations is often viewed as peripheral to the physics of interest, for
instance as an inconvenient source of scattering or decoherence. Here, we
present a comprehensive study on the longitudinal magneto-thermal transport in
a paramagnetic effective spin-1/2 magnetic insulator CsYbSe. We introduce a
minimal model requiring only Zeeman splitting and magnetoelastic coupling, and
use it to argue that hybridized excitations -- formed from acoustic phonons and
localized spin-flip-excitations across the Zeeman gap of the crystal electric
field ground doublet -- are responsible for a striking non-monotonic field
dependence of longitudinal thermal conductivity. Beyond highlighting a starring
role for phonons, our results raise the prospect of universal magneto-thermal
transport phenomena in magnetic insulators that originate from simple features
shared across many systems.Comment: 8 pages, 4 figure