Effect of the elastic modulus of the matrix on magnetostrictive strain in composites

The effect of the matrix material on the magnetostriction of composites containing highly magnetostrictive particles has been studied. Experimental results showed that the elastic modulus of the matrix is an important factor determining the bulk magnetostriction of the composite. For a series of composites with the same volume fraction of magnetostrictive particles but different matrix materials, the bulk magnetostriction was found to increase systematically with decreasing elastic modulus of the matrix. A modeltheory for the magnetostriction of such composites has been developed, based on two limiting assumptions: uniform strain or uniform stress inside the composite. The theory was then used to predict the magnetostriction of the entire material from the volume fractions of the components, their elastic moduli and magnetostrictions. These predictions were in agreement with the experimental results. It is concluded that to obtain a high magnetostriction and adequate mechanical properties of a composite, the elastic moduli of the magnetostrictive phase and the matrix should be as close as possible in value

Phase relationships and cation disorder in RE{sub 1+x}Ba{sub 2-x}Cu{sub 3}O{sub 7+{delta}}, RE = Pr, Nd, Sm, Gd

Unlike Y123 which forms only a stoichiometric compound, the light arare earth elements (LRE) form a solid solution LRE{sub 1+x}Ba{sub 2-x}Cu{sub 3}O{sub 7+{delta}} (LRE123ss), with increasing substitution of the LRE{sup 3+} for the Ba{sup 2+} as the ionic radii of the LRE increases. The sub-solidus phase relationships around the LRE123ss change for La, Pr and Nd, but are similar for Sm and Gd. However, the solubility limit decreases with decreasing ionic radii. In addition, the solubility limits for Sm and Gd are strongly influenced by PO{sub 2} during high temperature annealing. The range of solubility is, for any given LRE system, strongly dependent on the oxygen partial pressure (PO{sub 2}) providing a new means by which to control the microstructure in the RE123 system

Effect of the elastic modulus of the matrix on magnetostrictive strain in composites

The effect of the matrix material on the magnetostriction of composites containing highly magnetostrictive particles has been studied. Experimental results showed that the elastic modulus of the matrix is an important factor determining the bulk magnetostriction of the composite. For a series of composites with the same volume fraction of magnetostrictive particles but different matrix materials, the bulk magnetostriction was found to increase systematically with decreasing elastic modulus of the matrix. A modeltheory for the magnetostriction of such composites has been developed, based on two limiting assumptions: uniform strain or uniform stress inside the composite. The theory was then used to predict the magnetostriction of the entire material from the volume fractions of the components, their elastic moduli and magnetostrictions. These predictions were in agreement with the experimental results. It is concluded that to obtain a high magnetostriction and adequate mechanical properties of a composite, the elastic moduli of the magnetostrictive phase and the matrix should be as close as possible in value.The following article appeared in Applied Physics Letters 74 (1999): 1159 and may be found at http://dx.doi.org/10.1063/1.123473.</p

Suppression of superconductivity in the R(Ba<SUB>1-z</SUB>R<SUB>z</SUB>)<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7+&#948;</SUB> (R=Pr,Nd) system

Structural and superconducting behavior of samples prepared with the nominal compositions of Nd1.05(Ba1-zPrz)1.95Cu3O7+&#948; has been investigated by neutron-diffraction and dc magnetization measurements. Neutron data refined by the Reitveld method showed that there is mixing of the rare-earth (R) ions with a substantial fraction of the Pr going to the normal R site in the RBa2Cu3O7+&#948;-type structure and a corresponding fraction of the Nd going to the Ba site. Structural changes due to the trivalent R ions going to the Ba site are very similar to those observed in the Nd1+xBa2-xCu3O7+&#948;(Nd123ss), indicating that Pr behaves like other trivalent R's on the divalent Ba site. Magnetization measurements show that the depression in Tc is more pronounced for the Pr bearing samples than that for Nd123ss for the same number of trivalent ions on the Ba site. However, by correcting the changes in Tc for the depression associated with the fraction of Pr on the R site, the depression in Tc per trivalent ion on the divalent site is found to be identical to that in other light R123ss. Thus the depression in superconductivity in this series of samples is due to two independent effects: (1) Pr on the R site and (2) hole localization due to trivalent R ions on the Ba site. In this respect, Pr on the Ba site appears to behave like all the other trivalent R ions