In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

The area of artificial muscle is a highly interdisciplinary field of research that has evolved rapidly in the last 30 years. Recent advances in nanomaterial fabrication and characterization, specifically carbon nanotubes and nanowires, have had major contributions in the development of artificial muscles. However, what can artificial muscles really do for humans? This question is considered here by first examining nature's solutions to this design problem and then discussing the structure, actuation mechanism, applications, and limitations of recently developed artificial muscles, including highly oriented semicrystalline polymer fibers; nanocomposite actuators; twisted nanofiber yarns; thermally activated shape-memory alloys; ionic-polymer/metal composites; dielectric-elastomer actuators; conducting polymers; stimuli-responsive gels; piezoelectric, electrostrictive, magnetostrictive, and photostrictive actuators; photoexcited actuators; electrostatic actuators; and pneumatic actuators.

Artificial Muscles: Mechanisms, Applications, and Challenges.

A device, kit and method may employ an implantable device (e.g., annuloplasty implant) and a tool to implant such. The implantable device is positionable in a cavity of a bodily organ (e.g., a heart) and operable to constrict a bodily orifice (e.g., a mitral valve). Tissue anchors are guided into precise position by an intravascularly deployed anchor guide frame and embedded in an annulus. Constriction of the orifice may be accomplished via a variety of structures, for example by cinching a flexible cable or anchored annuloplasty ring, the cable or ring attached to the tissue anchors. The annuloplasty ring may be delivered in a generally elongated configuration, and implanted in an anchored generally arch, arcuate or annular configuration. Such may move a posterior leaflet anteriorly and an anterior leaflet posteriorly, improving leaflet coaptation to eliminate mitral regurgitation.

Medical device, kit and method for constricting tissue or a bodily orifice, for example, a mitral valve

There are provided a magnetoresistance effect element, a magnetic head, a magnetic head assembly and a magnetic recording system, which have high sensitivity and high reliability. The magnetoresistance effect element has two ferromagnetic layers, a non-magnetic layer provided between the ferromagnetic layers, and a layer containing an oxide or nitride as a principal component, wherein the layer containing the oxide or nitride as the principal component contains a magnetic transition metal element which does not bond to oxygen and nitrogen and which is at least one of Co, Fe and Ni.

Magnetoresistance effect element

A kinesthetic feedback apparatus and method whereby braking forces are imposed on a hand-movable lever The lever is either a joystick or a uniplanar lever, and the braking forces are imposed by a friction plate being pressed against a portion of the lever by a length of magnetostrictive material An electromagnetic coil around the magnetostrictive material receives a signal from a remote apparatus driven by movement of the lever The magnitude of the signal is a function of the resistive forces encountered by the remote apparatus so that the braking forces are directly proportional to the resistive forces thereby providing kinesthetic feedback to the person operating the lever

Kinesthetic feedback apparatus and method

Grain-oriented polycrystalline or single crystal magnetostrictive materialsn the general formula Tbx Dy1-x Fe2-w, Tbx Ho1-x Fe2-w, Smx Dy1-x Fex-w, Smx Ho1-x Fe2-w, Tbx Hoy Dyz Fe2-w, or Smx Hoy Dyz Fe2-w, wherein O≦w≦0.20, and x+y+z=1. X, y, and z are selected to maximize the magnetostrictive effect and the magnetomechanical coupling coefficient K33. These material may be used in magnetostrictive transducers, delay lines, variable frequency resonators, and filters.

Rare earth-iron magnetostrictive materials and devices using these materials

An elongate structure having a magnetostrictive material composition is subjected to tensile stress in the longitudinal-axial direction, thereby generally orienting the magnetization of the elongate structure in the longitudinal-axial direction. Electrical current is conducted through the elongate structure and/or through at least one adjacent elongate conductor, thereby generally orienting the magnetization of the elongate structure in the transverse direction, generally in parallel with the transverse direction of the magnetic field concomitant the conduction of current through the elongate structure. The elongate structure magnetostrictively contracts due to the (generally 90°) repositioning of the magnetization of the elongate structure. Examples of inventive configurational variants include: (i) an elongate structure itself conducting current; (ii) a hollow elongate structure accommodating placement therethrough of at least one elongate conductor; (iii) an elongate structure flanked by a pair of elongate conductors conducting current in opposite directions; (iv) plural elongate structures bordering a centralized elongate conductor.

High magnetostriction of positive magnetostrictive materials under tensile load

The objective of this work is to characterize the magnetoelastic transduction properties of single-crystal and textured polycrystalline Fe-Ga alloys (Galfenol) under controlled mechanical, magnetic, and thermal conditions. Polycrystalline samples of interest include a directionally solidified specimen, which possesses a favorable saturation magnetostriction output, and an extruded specimen, whose magnetostriction properties are significantly reduced by annealing. A brief discussion of the thermally controlled transducer used for the magnetic testing is presented first. Thereafter, the single-crystal response to major-loop cyclic magnetic fields under different temperature and stress conditions, as well as its response to minor-loop cyclic magnetic fields and major-loop cyclic stress are examined. Next, the magnetic and magnetostrictive responses to major-loop cyclic magnetic field conditions are compared for the directionally solidified, extruded, and single-crystal specimens. The paper concludes with a m...

Quasi-static Transduction Characterization of Galfenol

The objective of this work is to characterize the magnetoelastic transduction properties of single-crystal and textured polycrystalline Fe-Ga alloys (Galfenol) under controlled mechanical, magnetic, and thermal conditions. Polycrystalline samples of interest include a directionally solidified specimen, which possesses a favorable saturation magnetostriction output, and an extruded specimen, whose magnetostriction properties are significantly reduced by annealing. A brief discussion of the thermally controlled transducer used for the magnetic testing is presented first. Thereafter, the single-crystal response to major- loop cyclic magnetic fields under different temperature and stress conditions, as well as its response to minor-loop cyclic magnetic fields and major-loop cyclic stress are examined. Next, the magnetic and magnetostrictive responses to major-loop cyclic magnetic field conditions are compared for the directionally solidified, extruded, and single-crystal specimens. The paper concludes with a magnetic characterization summary of the different Fe-Ga alloys examined.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1056&context=ameslab_conf

Quasi-Static Transduction Characterization of Galfenol

The magnetostrictive rod of a linear motor is made of twinned single crys Terfenol-D having its crystalline axis aligned with the rod axis to produce non-uniform transverse magnetostriction during axial magnetostrictive elongation of the rod in response to a triggering magnetic field. Slide bearing forces applied through spring biased support plates are limited to flat surfaces formed on the rod perpendicular to a transverse axis along which the rod is magnetostrictively contracted.

Arthur E. Clark

Papers

Rare earth-iron magnetostrictive materials and devices using these materials

High magnetostriction of positive magnetostrictive materials under tensile load

Quasi-static Transduction Characterization of Galfenol

Quasi-Static Transduction Characterization of Galfenol

Magnetostrictive linear motor