7 research outputs found
Observation of Resonant Quantum Magnetoelectric Effect in a Multiferroic Metal–Organic Framework
A resonant quantum magnetoelectric
coupling effect has been demonstrated
in the multiferroic metal–organic framework of [(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>]ÂFeÂ(HCOO)<sub>3</sub>. This material shows
a coexistence of a spin-canted antiferromagnetic order and ferroelectricity
as well as clear magnetoelectric coupling below <i>T</i><sub>N</sub> ≈ 19 K. In addition, a component of single-ion
quantum magnets develops below ∼8 K because of an intrinsic
magnetic phase separation. The stair-shaped magnetic hysteresis loop
at 2 K signals resonant quantum tunneling of magnetization. Meanwhile,
the magnetic field dependence of dielectric permittivity exhibits
sharp peaks just at the critical tunneling fields, evidencing the
occurrence of resonant quantum magnetoelectric coupling effect. This
resonant effect enables a simple electrical detection of quantum tunneling
of magnetization
Enhanced Catalytic Activities of NiPt Truncated Octahedral Nanoparticles toward Ethylene Glycol Oxidation and Oxygen Reduction in Alkaline Electrolyte
The
high cost and poor durability of Pt nanoparticles (NPs) are great
limits for the proton exchange membrane fuel cells (PEMFCs) from being
scaled-up for commercial applications. Pt-based bimetallic NPs together
with a uniform distribution can effectively reduce the usage of expensive
Pt while increasing poison resistance of intermediates. In this work,
a simple one-pot method was used to successfully synthesize ultrafine
(about 7.5 nm) uniform NiPt truncated octahedral nanoparticles (TONPs)
in dimethylformamid (DMF) without any seeds or templates. The as-prepared
NiPt TONPs with Pt-rich surfaces exhibit greatly improved catalytic
activities together with good tolerance and better stability for ethylene
glycol oxidation reaction (EGOR) and oxygen reduction reaction (ORR)
in comparison with NiPt NPs and commercial Pt/C catalysts in alkaline
electrolyte. For example, the value of mass and specific activities
for EGOR are 23.2 and 17.6 times higher comparing with those of commercial
Pt/C, respectively. Our results demonstrate that the dramatic enhancement
is mainly attributed to Pt-rich surface, larger specific surface area,
together with coupling between Ni and Pt atoms. This developed method
provides a promising pathway for simple preparation of highly efficient
electrocatalysts for PEMFCs in the near future
Observation of Resonant Quantum Magnetoelectric Effect in a Multiferroic Metal–Organic Framework
A resonant quantum magnetoelectric
coupling effect has been demonstrated
in the multiferroic metal–organic framework of [(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>]ÂFeÂ(HCOO)<sub>3</sub>. This material shows
a coexistence of a spin-canted antiferromagnetic order and ferroelectricity
as well as clear magnetoelectric coupling below <i>T</i><sub>N</sub> ≈ 19 K. In addition, a component of single-ion
quantum magnets develops below ∼8 K because of an intrinsic
magnetic phase separation. The stair-shaped magnetic hysteresis loop
at 2 K signals resonant quantum tunneling of magnetization. Meanwhile,
the magnetic field dependence of dielectric permittivity exhibits
sharp peaks just at the critical tunneling fields, evidencing the
occurrence of resonant quantum magnetoelectric coupling effect. This
resonant effect enables a simple electrical detection of quantum tunneling
of magnetization
Thermal Stability of Skyrmion Tubes in Nanostructured Cuboids
Magnetic skyrmions in bulk materials
are typically regarded as
two-dimensional structures. However, they also exhibit three-dimensional
configurations, known as skyrmion tubes, that elongate and extend
in-depth. Understanding the configurations and stabilization mechanism
of skyrmion tubes is crucial for the development of advanced spintronic
devices. However, the generation and annihilation of skyrmion tubes
in confined geometries are still rarely reported. Here, we present
direct imaging of skyrmion tubes in nanostructured cuboids of a chiral
magnet FeGe using Lorentz transmission electron microscopy (TEM),
while applying an in-plane magnetic field. It is observed that skyrmion
tubes stabilize in a narrow field-temperature region near the Curie
temperature (Tc). Through a field cooling
process, metastable skyrmion tubes can exist in a larger region of
the field-temperature diagram. Combining these experimental findings
with micromagnetic simulations, we attribute these phenomena to energy
differences and thermal fluctuations. Our results could promote topological
spintronic devices based on skyrmion tubes
Tailoring of the Interfacial Dzyaloshinskii–Moriya Interaction in Perpendicularly Magnetized Epitaxial Multilayers by Crystal Engineering
The interplay between the interfacial crystalline structure
and
Dzyaloshinskii–Moriya interaction (DMI) was investigated by
Fe insertion in epitaxial Pt/Co/Ir perpendicular magnetized multilayers.
The experimental results with the support of first-principles calculation
indicate that the Fe/Ir interface exhibits a positive interfacial
DMI (iDMI) originating from the fcc crystalline structure inserted
by 2 monolayers (ML) Fe, while a negative one from the structure with
a layer shifting of 1-ML Fe insertion. The total iDMI of the multilayers
increases (decreases) due to the additive enhancement (competitive
counteraction) between the iDMI of Fe/Ir and Pt/Co interfaces. Comparing
the iDMI of single-crystalline and textured multilayers, the iDMI
of multilayers is found to be particularly sensitive to the crystallinity
nearby the heterointerfaces. This work is of vital importance to reveal
a deeper insight into the physical mechanism of the iDMI and provides
a viable strategy for tailoring the iDMI of the multilayers by crystal
engineering
Real-Space Observation of Nonvolatile Zero-Field Biskyrmion Lattice Generation in MnNiGa Magnet
Magnetic
skyrmions, particular those without the support of external
magnetic fields over a wide temperature region, are promising as alternative
spintronic units to overcome the fundamental size limitation of conventional
magnetic bits. In this study, we use in situ Lorentz microscope to
directly demonstrate the generation and sustainability of robust biskyrmion
lattice at zero magnetic field over a wide temperature range of 16–338
K in MnNiGa alloy. This procedure includes a simple field-cooling
manipulation from 360 K (higher than Curie temperature <i>T</i><sub>C</sub> ∼ 350 K), where topological transition easily
occurs by adapting the short-range magnetic clusters under a certain
magnetic field. The biskyrmion phase is favored upon cooling below <i>T</i><sub>C</sub>. Once they are generated, the robust high-density
biskyrmions persist even after removing the external magnetic field
due to the topological protection and the increased energy barrier
Controllable Spin–Orbit Torque Induced by Interfacial Ion Absorption in Ta/CoFeB/MgO Multilayers with Canted Magnetizations
Electrically generated spin–orbit torque (SOT)
has emerged
as a powerful pathway to control magnetization for spintronic applications
including memory, logic, and neurocomputing. However, the requirement
of external magnetic fields, together with the ultrahigh current density,
is the main obstacle for practical SOT devices. In this paper, we
report that the field-free SOT-driven magnetization switching can
be successfully realized by interfacial ion absorption in perpendicular
Ta/CoFeB/MgO multilayers. Besides, the tunable SOT efficiency exhibits
a strong dependence on interfacial Ti insertion thicknesses. Polarized
neutron reflection measurements demonstrate the existence of canted
magnetization with Ti inserted, which leads to deterministic magnetization
switching. In addition, interfacial characterization and first-principles
calculations reveal that B absorption by the Ti layer is the main
cause behind the enhanced interfacial transparency, which determines
the tunable SOT efficiency. Our findings highlight an attractive scheme
to a purely electric control spin configuration, enabling innovative
designs for SOT-based spintronics via interfacial engineering