178 research outputs found
Prospect for antiferromagnetic spintronics
Exploiting both spin and charge of the electron in electronic micordevices
has lead to a tremendous progress in both basic condensed-matter research and
microelectronic applications, resulting in the modern field of spintronics.
Current spintronics relies primarily on ferromagnets while antiferromagnets
have traditionally played only a supporting role. Recently, antiferromagnets
have been revisited as potential candidates for the key active elements in
spintronic devices. In this paper we review approaches that have been employed
for reading, writing, and storing information in antiferromagnets
Magnetization Reversal by Electric-Field Decoupling of Magnetic and Ferroelectric Domains Walls in Multiferroic-Based Heterostructures
We demonstrate that the magnetization of a ferromagnet in contact with an
antiferromagnetic multiferroic (LuMnO3) can be speedily reversed by electric
field pulsing, and the sign of the magnetic exchange bias can switch and
recover isothermally. As LuMnO3 is not ferroelastic, our data conclusively show
that this switching is not mediated by strain effects but is a unique
electric-field driven decoupling of the ferroelectric and ferromagnetic domains
walls. Their distinct dynamics are essential for the observed magnetic
switching
Storing magnetic information in IrMn/MgO/Ta tunnel junctions via field-cooling
In this paper, we demonstrate that in Ta/MgO/IrMn tunneling junctions, containing no ferromagnetic elements, distinct metastable resistance states can be set by field cooling the devices from above the NĂ©el temperature (TN) along different orientations. Variations of the resistance up to 10% are found upon field cooling in applied fields, in-plane or out-of-plane. Well below TN, these metastable states are insensitive to magnetic fields up to 2 T, thus constituting robust memory states. Our work provides the demonstration of an electrically readable magnetic memory device, which contains no ferromagnetic elements and stores the information in an antiferromagnetic active layer
Investigation of magneto-structural phase transition in FeRh by reflectivity and transmittance measurements in visible and near-infrared spectral region
Magneto-structural phase transition in FeRh epitaxial layers was studied optically. It is shown that the transition between the low-temperature antiferromagnetic phase and the high-temperature ferromagnetic phase is accompanied by a rather large change of the optical response in the visible and near-infrared spectral ranges. This change is consistent with ab initio calculations of reflectivity and transmittance. Phase transition temperatures in a series of FeRh films with thicknesses ranging from 6 to 100 nm is measured thereby demonstrating the utility of the method to quickly characterise samples. Spatially resolved imaging of their magnetic properties with a micrometer resolution shows that the phase transition occurs at different temperatures in different parts of the sample
Antiferromagnetic spintronics
Antiferromagnetic materials are magnetic inside, however, the direction of
their ordered microscopic moments alternates between individual atomic sites.
The resulting zero net magnetic moment makes magnetism in antiferromagnets
invisible on the outside. It also implies that if information was stored in
antiferromagnetic moments it would be insensitive to disturbing external
magnetic fields, and the antiferromagnetic element would not affect
magnetically its neighbors no matter how densely the elements were arranged in
a device. The intrinsic high frequencies of antiferromagnetic dynamics
represent another property that makes antiferromagnets distinct from
ferromagnets. The outstanding question is how to efficiently manipulate and
detect the magnetic state of an antiferromagnet. In this article we give an
overview of recent works addressing this question. We also review studies
looking at merits of antiferromagnetic spintronics from a more general
perspective of spin-ransport, magnetization dynamics, and materials research,
and give a brief outlook of future research and applications of
antiferromagnetic spintronics.Comment: 13 pages, 7 figure
Room-temperature antiferromagnetic memory resistor
The bistability of ordered spin states in ferromagnets (FMs) provides the
magnetic memory functionality. Traditionally, the macroscopic moment of ordered
spins in FMs is utilized to write information on magnetic media by a weak
external magnetic field, and the FM stray field is used for reading. However,
the latest generation of magnetic random access memories demonstrates a new
efficient approach in which magnetic fields are replaced by electrical means
for reading and writing. This concept may eventually leave the sensitivity of
FMs to magnetic fields as a mere weakness for retention and the FM stray fields
as a mere obstacle for high-density memory integration. In this paper we report
a room-temperature bistable antiferromagnetic (AFM) memory which produces
negligible stray fields and is inert in strong magnetic fields. We use a
resistor made of an FeRh AFM whose transition to a FM order 100 degrees above
room-temperature, allows us to magnetically set different collective directions
of Fe moments. Upon cooling to room-temperature, the AFM order sets in with the
direction the AFM moments pre-determined by the field and moment direction in
the high temperature FM state. For electrical reading, we use an
antiferromagnetic analogue of the anisotropic magnetoresistance (AMR). We
report microscopic theory modeling which confirms that this archetypical
spintronic effect discovered more than 150 years ago in FMs, can be equally
present in AFMs. Our work demonstrates the feasibility to realize
room-temperature spintronic memories with AFMs which greatly expands the
magnetic materials base for these devices and offers properties which are
unparalleled in FMs
Hidden magnetic states emergent under electric field, in a room temperature composite magnetoelectric multiferroic
The ability to control a magnetic phase with an electric field is of great current interest for a variety of low power electronics in which the magnetic state is used either for information storage or logic operations. Over the past several years, there has been a considerable amount of research on pathways to control the direction of magnetization with an electric field. More recently, an alternative pathway involving the change of the magnetic state (ferromagnet to antiferromagnet) has been proposed. In this paper, we demonstrate electric field control of the Anomalous Hall Transport in a metamagnetic FeRh thin film, accompanying an antiferromagnet (AFM) to ferromagnet (FM) phase transition. This approach provides us with a pathway to "hide" or "reveal" a given ferromagnetic region at zero magnetic field. By converting the AFM phase into the FM phase, the stray field, and hence sensitivity to external fields, is decreased or eliminated. Using detailed structural analyses of FeRh films of varying crystalline quality and chemical order, we relate the direct nanoscale origins of this memory effect to site disorder as well as variations of the net magnetic anisotropy of FM nuclei. Our work opens pathways toward a new generation of antiferromagnetic - ferromagnetic interactions for spintronics
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