1,727 research outputs found
Design of compensated ferrimagnetic Heusler alloys for giant tunable exchange bias
The discovery of materials with improved functionality can be accelerated by
rational material design. Heusler compounds with tunable magnetic sublattices
allow to implement this concept to achieve novel magnetic properties. Here, we
have designed a family of Heusler alloys with a compensated ferrimagnetic
state. In the vicinity of the compensation composition in Mn-Pt-Ga, a giant
exchange bias (EB) of more than 3 T and a similarly large coercivity are
established. The large exchange anisotropy originates from the exchange
interaction between the compensated host and ferrimagnetic clusters that arise
from intrinsic anti-site disorder. We demonstrate the applicability of our
design concept on a second material, Mn-Fe-Ga, with a magnetic transition above
room temperature, exemplifying the universality of the concept and the
feasibility of room-temperature applications. Our study points to a new
direction for novel magneto-electronic devices. At the same time it suggests a
new route for realizing rare-earth free exchange-biased hard magnets, where the
second quadrant magnetization can be stabilized by the exchange bias.Comment: Four figure
Magnetic properties of triangular lattice antiferromagnets Ba3RB9O18 (R = Yb, Er)
Frustration, spin correlations and interplay between competing degrees of
freedom are some of the key ingredients that underlie exotic states with
fractional excitations in quantum materials. Rare-earth based two dimensional
magnetic lattice wherein crystal electric field, spin-orbit coupling,
anisotropy and electron correlation between rare-earth moments offer a new
paradigm in this context. Herein, we present crystal structure, magnetic
susceptibility and specific heat accompanied by crystal electric field
calculations on the polycrystalline sample of Ba3RB9O18 (R = Yb, Er) in which
R3+ ions form a perfect triangular lattice without anti-site disorder. The
localized R3+ spins show neither long-range order nor spin-glass state down to
1.9 K in Ba3RB9O18. Magnetization data reveal a pseudospin Jeff = 1/2 ( Yb3+)
in the Kramers doublet state and a weak antiferromagnetic interaction between
Jeff = 1/2 moments in the Yb variant. On the other hand, the effective moment
{\mu}eff = 8.8 {\mu}B was obtained from the Curie-Weiss fit of the
low-temperature susceptibility data of Er variant suggests the admixture of
higher crystal electric field states with the ground state. The Curie-Weiss fit
of low-temperature susceptibility data for Er system unveils the presence of a
relatively strong antiferromagnetic interaction between Er3+ moments compared
to its Yb3+ analog. Ba3ErB9O18 does not show long-range magnetic ordering down
to 500 mK. Furthermore, our crystal electric field calculations based on
magnetization data of Ba3ErB9O18 suggest the presence of a small gap between
the ground and first excited Kramers doublets. The broad maximum around 4 K in
magnetic specific heat in zero-field is attributed to the thermal population of
the first CEF excited state in Ba3ErB9O18, which is consistent with our CEF
calculations
Magnetism and field-induced effect in a spin-orbit entangled Jeff = 1/2 honeycomb lattice
The interplay between spin-orbit coupling, frustration-induced anisotropic
magnetic interaction, and spin correlations can lead to novel states with
exotic excitations in rare-earth-based quantum magnets. Herein, we present the
crystal structure, magnetization, electron spin resonance (ESR), specific heat,
and nuclear magnetic resonance (NMR) experiments on the polycrystalline samples
of Ba9Yb2Si6O24 in which Yb3+ ions form a perfect honeycomb lattice without
detectable anti-site disorder. Magnetization data reveal antiferromagnetically
coupled spin-orbit entangled Jeff = 1/2 degrees of freedom of Yb3+ ions in the
Kramers doublet state where the Curie-Weiss temperature is - 2.97 K, as
obtained from the low-temperature magnetic susceptibility data. The ESR
measurements reveal that the first excited Kramers doublet is 32.3(7) meV above
the ground state. The specific heat results suggest the presence of an
antiferromagnetic phase transition at 2.26 K. The long-range antiferromagnetic
order is completely suppressed upon the application of magnetic field and a
field-induced disordered state is observed in an applied magnetic field of 2.5
T, which is also confirmed by NMR measurements. Furthermore, the NMR
spin-lattice relaxation rate reveals the presence of a field-induced gap that
is attributed to the Zeeman splitting of Kramers doublet state in this quantum
material. Our experiments suggest the presence of a phase transition and
short-range spin correlations appearing well above the antiferromagnetic phase
transition temperature and a field-induced disordered state in this spin-orbit
entangled Jeff =1/2 rare-earth magnet on a honeycomb lattice
Towards More Specific Personality Research in Entrepreneurship: Relating Conscientiousness Facets to Venture Performance
Purpose. The literature has long recognized the importance of the conscientious entrepreneurial personality. This study explores how seven of its facets/sub-dimensions (Achievement-Striving, Efficiency, Responsibility, Industriousness, Self-Control, Conventionality, and Persistence) relate to three performance outcomes (Ventures Started, Years at Current Venture, and Annual Sales.)
Design/methodology/approach. 166 active entrepreneurs were surveyed via an entrepreneurship center at a Western US university. Data was then modeled via Ordinary Least Squares to obtain regression estimates for the dependent variables.
Findings. Counter to expectations, results indicate that facet measures relate very differently in terms of magnitude, direction, and significance to the performance outcomes. These more nuanced relations are lost when using broad/aggregate dimensional measures.
Research implications. Broad personality measures, as conventionally used, are suboptimal for entrepreneurial research as they potentially yield misleading results. Studies should instead apply the more-specific facet measures, which offer more accurate personality assessments.
Practical implications. Practitioners should also use the more-specific facet measures. Doing so will be of value across a variety of public, private, and educational settings.
Originality/Value. For decades, entrepreneurship has addressed the effects of broad/aggregate personality dimensions. This article is the first to approach the entrepreneurial personality from a more-specific facet level, an approach offering substantial research opportunities
Experimental signatures of quantum and topological states in frustrated magnetism
Frustration in magnetic materials arising from competing exchange
interactions can prevent the system from adopting long-range magnetic order and
can instead lead to a diverse range of novel quantum and topological states
with exotic quasiparticle excitations. Here, we review prominent examples of
such emergent phenomena, including magnetically-disordered and extensively
degenerate spin ices, which feature emergent magnetic monopole excitations,
highly-entangled quantum spin liquids with fractional spinon excitations,
topological order and emergent gauge fields, as well as complex particle-like
topological spin textures known as skyrmions. We provide an overview of recent
advances in the search for magnetically-disordered candidate materials on the
three-dimensional pyrochlore lattice and two-dimensional triangular, kagome and
honeycomb lattices, the latter with bond-dependent Kitaev interactions, and on
lattices supporting topological magnetism. We highlight experimental signatures
of these often elusive phenomena and single out the most suitable experimental
techniques that can be used to detect them. Our review also aims at providing a
comprehensive guide for designing and investigating novel frustrated magnetic
materials, with the potential of addressing some important open questions in
contemporary condensed matter physics
119Sn solid state NMR and M\"ossbauer spectroscopic studies of the intermediate-valent stannide CeRuSn
The ternary stannide CeRuSn is a static mixed-valent cerium compound with an
or-dering of trivalent and intermediate-valent cerium on two distinct
crystallographic sites. 119Sn M\"ossbauer spectra showed two electronically
almost identical tin atoms at 323 K, while at 298 K and below (77 and 4.2 K)
two tin sites can clearly be distinguished. 119Sn solid state NMR experiments
are performed to probe the local hyperfine fields at the two different Sn
sites. 119Sn NMR powder spectra are nicely fitted with two Sn sites with nearly
the same magnetic anisotropy, but with different absolute shift values. Both Sn
sites are strongly affected by crossover-like transitions between 100 and 280
K. This local-site study confirms the superstructure modulations found in
previous investiga-tions. Towards lower temperatures the powder spectra are
broadened giving strong evidence for the antiferromagnetically ordered ground
state
Magnetization and spin dynamics of the spin S=1/2 hourglass nanomagnet Cu5(OH)2(NIPA)4*10H2O
We report a combined experimental and theoretical study of the spin S=1/2
nanomagnet Cu5(OH)2(NIPA)4*10H2O (Cu5-NIPA). Using thermodynamic, electron spin
resonance and 1H nuclear magnetic resonance measurements on one hand, and ab
initio density-functional band-structure calculations, exact diagonalizations
and a strong coupling theory on the other, we derive a microscopic magnetic
model of Cu5-NIPA and characterize the spin dynamics of this system. The
elementary five-fold Cu2+ unit features an hourglass structure of two
corner-sharing scalene triangles related by inversion symmetry. Our microscopic
Heisenberg model comprises one ferromagnetic and two antiferromagnetic exchange
couplings in each triangle, stabilizing a single spin S=1/2 doublet ground
state (GS), with an exactly vanishing zero-field splitting (by Kramer's
theorem), and a very large excitation gap of \Delta~68 K. Thus, Cu5-NIPA is a
good candidate for achieving long electronic spin relaxation (T1) and coherence
(T2) times at low temperatures, in analogy to other nanomagnets with low-spin
GS's. Of particular interest is the strongly inhomogeneous distribution of the
GS magnetic moment over the five Cu2+ spins. This is a purely
quantum-mechanical effect since, despite the non-frustrated nature of the
magnetic couplings, the GS is far from the classical collinear ferrimagnetic
configuration. Finally, Cu5-NIPA is a rare example of a S=1/2 nanomagnet
showing an enhancement in the nuclear spin-lattice relaxation rate 1/T1 at
intermediate temperatures.Comment: 18 pages, 16 figures, 3 table
A strategic value appropriation path for cloud computing
Cloud-based information management is one of the leading competitive differentiation strategies for firms. With the increasing criticality of information management in value creation and process support, establishing an integrated capability with cloud computing is vital for organizational success in the changing landscape of business competition. These issues have received scant attention, however. We draw on the resource-based view, dynamic capability hierarchy concepts, and the perspective of operand and operant resources to suggest a cloud value appropriation model for firms. We argue that, to appropriate business value from cloud computing, the firm needs to effectively deploy cloud computing and leverage cloud operant resources as firm capabilities in a hierarchical fashion toward the development of cloud computing-based service models in order to reliably achieve the desired business outcomes. We propose a model encompassing the principles of infrastructure and cloud platform deployment, integration and service orientation, and alignment with business processes that explain the linkage from cloud computing to firm performance. We test this approach to value creation with a cloud computing implementation assessment model using a sample of 147 firms that have implemented cloud computing in India. Our analysis uncovers a strategic value appropriation path from cloud technological capability to firm performance via cloud integration capability, cloud service portfolio capability, and business flexibility. This research offers new insights regarding the underlying mechanisms for how cloud computing affects firm performance via cloud-enabled capabilities and the business functions that are supported by cloud capabilities
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