Government of the United States of America, As Represented by the Secretary of Commerce

Robert D Shull

Alexander J Shapiro

Virgil Provenzano

Joseph J Ritter

Daniel B Gopman

Lawrence H Bennett

A magnetic piezoelectric composite adjusts magnetic anisotropy strength in a bimetallic member and includes: a piezoelectric layer to produce a strain in response to receipt of a strain voltage; and the bimetallic member disposed on the piezoelectric layer, the bimetallic member including: a plurality of metal layers, such that a second metal layer is interposed between a pair of first metal layers, the bimetallic member being ferromagnetic; and a magnetic anisotropy strength that changes in response to receipt of the strain from the piezoelectric layer.

Magnetic piezoelectric composite, sensor, and memory

A GdGeSirefrigerant compound is doped or alloyed with an effective amount of silicide-forming metal element such that the magnetic hysteresis losses in the doped GdGeSicompound are substantially reduced in comparison to the hysteresis losses of the undoped GdGeSicompound. The hysteresis losses can be nearly eliminated by doping the GdGeSicompound with iron, cobalt, manganese, copper, or gallium. The effective refrigeration capacities of the doped GdGeSicompound are significantly higher than for the undoped GdGeSicompound.

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A nanocomposite superparamagnetic material that includes nanosize particles of a magnetic component, preferably a rare earth and a transition element, dispersed finely within a bulk matrix component provides finely dispersed magnetic clusters, whereby a high magnetocaloric effect is obtained in using the nanocomposite material in a conventional magnetic refrigeration system. In one aspect of the present invention, an element formed of such a nanocomposite superparamagnetic material is reciprocated into and out of a heat exchanger within a controlled magnetic field and is in heat transfer communication with a second heat exchanger to facilitate the production of a refrigeration heat transfer effect thereby. In another aspect of the present invention, a generally disk-like element formed of the nanocomposite superparamagnetic material is rotated so that portions thereof move between a first heat exchanger and a second heat exchanger that is within a controlled magnetic field, to thereby perform refrigeration heat transfer between the two heat exchangers.

Nanocomposite material for magnetic refrigeration and superparamagnetic

A chemical process for producing bulk quantities of an iron-silica gel composite in which particle size, form, and magnetic state of the iron can be selected. The process involves polymerizing an ethanolic solution of tetraethylorthosilicate, ferric nitrate and water at low temperature under the influence of an HF catalyst. The chemical and magnetic states of the iron in the resultant composite are modified in situ by exposure to suitable oxidizing or reducing agents at temperatures under 400.degree. C. Iron-containing particles of less than 200 .ANG. diameter, homogeneously dispersed in silica matrices may be prepared in paramagnetic, superparamagnetic, ferrimagnetic and ferromagnetic states.

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Boyds, MD, United States of America

Robert D Shull