53 research outputs found
Domain periodicity in an easy-plane antiferromagnet with Dzyaloshinskii-Moriya interaction
Antiferromagnetic spintronics is a promising emerging paradigm to develop
high-performance computing and communications devices. From a theoretical point
of view, it is important to implement simulation tools that can support a
data-driven development of materials having specific properties for particular
applications. Here, we present a study focusing on antiferromagnetic materials
having an easy-plane anisotropy and interfacial Dzyaloshinskii-Moriya
interaction (IDMI). An analytical theory is developed and benchmarked against
full numerical micromagnetic simulations, describing the main properties of the
ground state in antiferromagnets and how it is possible to estimate the IDMI
from experimental measurements. The effect of the IDMI on the electrical
switching dynamics of the antiferromagnetic element is also analyzed. Our
theoretical results can be used for the design of multi-terminal heavy
metal/antiferromagnet memory devices
Probabilistic computing with voltage-controlled dynamics in magnetic tunnel junctions
Probabilistic (p-) computing is a physics-based approach to addressing computational problems
which are difficult to solve by conventional von Neumann computers. A key requirement for
p-computing is the realization of fast, compact, and energy-efficient probabilistic bits. Stochastic
magnetic tunnel junctions (MTJs) with low energy barriers, where the relative dwell time in each
state is controlled by current, have been proposed as a candidate to implement p-bits. This
approach presents challenges due to the need for precise control of a small energy barrier across
large numbers of MTJs, and due to the need for an analog control signal. Here we demonstrate
an alternative p-bit design based on perpendicular MTJs that uses the voltage-controlled
magnetic anisotropy (VCMA) effect to create the random state of a p-bit on demand. The MTJs
are stable (i.e. have large energy barriers) in the absence of voltage, and VCMA-induced
dynamics are used to generate random numbers in less than 10 ns/bit. We then show a compact
method of implementing p-bits by using VC-MTJs without a bias current. As a demonstration of
the feasibility of the proposed p-bits and high quality of the generated random numbers, we solve
up to 40 bit integer factorization problems using experimental bit-streams generated by VCMTJs. Our proposal can impact the development of p-computers, both by supporting a fully
spintronic implementation of a p-bit, and alternatively, by enabling true random number
generation at low cost for ultralow-power and compact p-computers implemented in
complementary metal-oxide semiconductor chips
A magneto-mechanical accelerometer based on magnetic tunnel junctions
Accelerometers have widespread applications and are an essential component in
many areas such as automotive, consumer electronics and industrial
applications. Most commercial accelerometers are based on
micro-electromechanical system (MEMS) that are limited in downscaling and power
consumption. Spintronics-based accelerometers have been proposed as
alternatives, however, current proposals suffer from design limitations that
result in reliability issues and high cost. Here we propose spintronic
accelerometers with magnetic tunnel junctions (MTJs) as building block, which
map accelerations into a measurable voltage across the MTJ terminals. The
device exploits elastic and dipolar coupling as a sensing mechanism and the
spintronic diode effect for the direct read out of the acceleration. The
proposed technology represents a potentially competitive and scalable solution
to current capacitive MEMS-based approaches that could lead to a step forward
in many of the commercial applications.Comment: main document with 4 figures + supplemental informatio
Ultralow-current-density and bias-field-free spin-transfer nano-oscillator
The spin-transfer nano-oscillator (STNO) offers the possibility of using the
transfer of spin angular momentum via spin-polarized currents to generate
microwave signals. However, at present STNO microwave emission mainly relies on
both large drive currents and external magnetic fields. These issues hinder the
implementation of STNOs for practical applications in terms of power
dissipation and size. Here, we report microwave measurements on STNOs built
with MgO-based magnetic tunnel junctions having a planar polarizer and a
perpendicular free layer, where microwave emission with large output power,
excited at ultralow current densities, and in the absence of any bias magnetic
fields is observed. The measured critical current density is over one order of
magnitude smaller than previously reported. These results suggest the
possibility of improved integration of STNOs with complementary
metal-oxide-semiconductor technology, and could represent a new route for the
development of the next-generation of on-chip oscillators.Comment: 18 pages, 4 figure
Voltage-Induced Ferromagnetic Resonance in Magnetic Tunnel Junctions
We demonstrate excitation of ferromagnetic resonance in CoFeB/MgO/CoFeB
magnetic tunnel junctions (MTJs) by the combined action of voltage-controlled
magnetic anisotropy (VCMA) and spin transfer torque (ST). Our measurements
reveal that GHz-frequency VCMA torque and ST in low-resistance MTJs have
similar magnitudes, and thus that both torques are equally important for
understanding high-frequency voltage-driven magnetization dynamics in MTJs. As
an example, we show that VCMA can increase the sensitivity of an MTJ-based
microwave signal detector to the sensitivity level of semiconductor Schottky
diodes.Comment: 5 pages; supplementary material adde
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