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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

BaFe 4 O 7 and K 0.22 Ba 0.89 Fe 4 O 7 : Canted Antiferromagnetic Diferrites with Exceptionally High Magnetic Ordering Temperatures [BaFe 4 O 7 and K 0.22 Ba 0.89 Fe 4 O 7 – New Canted Antiferromagnetic Diferrites with Exceptionally High Magnetic Ordering Temperatures]

Here, complex iron containing oxides, typically referred to as ferrites, have been extensively studied for their electronic and magnetic properties, including magnetotransport, ferromagnetism, ferroelectricity, and a combination of the latter two, known as multiferroism. The search for materials possessing simultaneous ferromagnetic and ferroelectric behavior is of significant interest both for the advancement of fundamental science and for applications in random access memory (RAM). Despite the great technological potential of multiferroics, one or both of the ferroic ordering temperatures tend to fall below room temperature, such as in the compositions TbMnO 3 and Ni 3 V 2 O 8 , thus eliminating their practical utility for RAM applications. The scarcity of multiferroics possessing room temperature ferroic orderings continues to drive exploratory research in this field. For this reason, ferrites have garnered significant interest due to their often high ferroic ordering temperatures, for example in BiFeO 3 . Among all ferrites, hexaferrites are the most studied prototypical examples and constitute a specific subclass of ferrites that follows the stoichiometry Ba O– n Fe 2 O 3 , in which the n value dictates the nomenclature, i.e., ( n = 6) is a hexaferrite or ( n = 1) is a monoferrite. This versatile class of materials encompasses a wide range of related structures best described by Pullar, serving as the motivation for this work.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Field-induced decays in XXZ triangular-lattice antiferromagnets

In this work, we investigate field-induced transformations in the dynamical response of the XXZ model on the triangular lattice that are associated with the anharmonic magnon coupling and decay phenomena. A set of concrete theoretical predictions is made for a close physical realization of the spin-1/2 XXZ model, Ba 3 CoSb 2 O 9 . We demonstrate that dramatic modifications in magnon spectrum must occur in low out-of-plane fields that are easily achievable for this material. The hallmark of the effect is a coexistence of the clearly distinct well-defined magnon excitations with significantly broadened ones in different regions of the k–ω space. The field-induced decays are generic for this class of models and become more prominent at larger anisotropies and in higher fields.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗