摘要:

To determine how the ac and dc magnetic properties are affected by elastic strain, the magnetic properties in the rolling direction of Epstein strips of elastically bent grain‐oriented 3% silicon iron were measured in an Epstein frame and in a Carr single‐strip permeameter. As the degree of bending becomes more pronounced, the coercive force and the ac core loss increase and the permeability decreases. The domain theory gives a rather simple approximate interpretation of the permeability data for magnetic intensities between one and ten oersteds.

ISSN:0021-8979    

DOI:10.1063/1.1723138

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Magnetic properties of a nickel‐zinc ferrite (15% NiO, 35% ZnO, 50% Fe2O3) were measured over a temperature range of 23°C to 110°C at hydrostatic pressures up to 40 000 psi.The relation between the shift in Curie temperature, &Dgr;Tc, and the change in pressure, &Dgr;p, was empirically found to be&Dgr;Tc=0.078(&Dgr;p)0.316.It is shown that if magnetic anisotropy and internal strains limit the magnetizing processes, the relation between coercive force,Hc, maximum flux density,Bm, and initial permeability, &mgr;0, is given byHc=&dgr;Bm/&mgr;0,where &dgr; is a proportionality constant. The experimental results obtained over the entire range of temperature and pressure verify the above relation. The value of &dgr; is 2.56 for the ferrite investigated.

ISSN:0021-8979    

DOI:10.1063/1.1723139

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The abnormal plots of reduced magnetizationvstemperature for ferrites containing zinc are found to be associated with a concentration gradient in zinc that is generated by the preferential loss of zinc during sintering. The variation of the gradient in samples of zinc‐iron spinels is correlated with sintering and annealing treatment and with sample dimensions.

ISSN:0021-8979    

DOI:10.1063/1.1723140

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A study has been made of the magnetic properties of the system of quenched magnesium ferrites (MgxIIFe1−xIII) · (Mg1−xIIFe1+xIII)O4, wherex, the fraction of magnesium ions in tetrahedral sites, varies from 0.14 to 0.26. Included among the properties examined are: saturation moment, Curie point, initial permeability, and coercive force. A limited study of the kinetics of the cation redistribution has also been made. Samples quenched from 1100°C and then tempered at 600°C require somewhat less than 16 hours to attain an equilibrium cation distribution at the latter temperature. The approach to equilibrium is consistent with a model in which the rate of approach is proportional toexp(−&thgr;0′+&thgr;1′x)/Twhere &thgr;0′ and &thgr;1′ are activation constants.

ISSN:0021-8979    

DOI:10.1063/1.1723141

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Because both manganese and iron assume multiple valences in oxide structures, it is possible to fabricate spinels over a continuous range of composition from Mn3O4to Fe3O4. Magnetic‐moment data for samples fabricated within this range are reported and an interpretation of the data in terms of the distribution of ions of manganese and iron is presented.The data agree with previous indications that manganese ferrite, MnFe2O4, is an almost completely normal spinel with Mn2+onAsites and Fe3+onBsites. In addition, the usual assumption that excess iron replaces manganese as Fe2+onBsites is substantiated. However, the data are not compatible with the previously held assumption that Fe3+is replaced by excess manganese as Mn3+. Instead, the variation of magnetic moments and Curie temperatures with composition is interpreted in terms of a model in which excess manganese replaces Fe3+as Mn4+and an equal amount of iron is converted to Fe2+. When the manganese content gets so high that all the iron is Fe2+(Mn2FeO4), manganese then replaces the iron as Mn3+and reconverts an equal amount of Mn4+to Mn3+, and the Mn3+, because of its tetragonal nature, introduces spinel twinning.It is proposed that the Mn4+&sngbnd;Fe2+pair in octahedral coordination is stabilized with respect to a Mn3+&sngbnd;Fe3+pair because of the interaction of the manganese orbitals with the 2porbitals of the surrounding oxygen anions.

ISSN:0021-8979    

DOI:10.1063/1.1723142

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

In yttrium‐iron garnet, iron may be entirely replaced by aluminum and gallium; chromium, scandium, and indium may be substituted for iron to a limited extent. Substitution proceeds on a steric basis for the nonmagnetic ions: Al3+and Ga3+, which are smaller than Fe3+, preferentially occupy the smaller, tetrahedrally coordinated positions, 24(d); the Sc3+and In3+ions, which are larger than Fe3+, preferentially occupy the larger, octahedrally coordinated positions, 16(a). The Cr3+ion, though smaller than Fe3+, preferentially occupies the octahedral position, presumably because of its electronic configuration. The magnetic moment initially increases with octahedral substitution and decreases with tetrahedral substitution. The Curie temperature is decreased by the substitution of nonmagnetic ions for iron as a consequence of the decrease in the number of Fe3+&sngbnd;O2−&sngbnd;Fe3+interactions.

ISSN:0021-8979    

DOI:10.1063/1.1723143

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Crystallographic and magnetic measurements of the system Li+xNi++1−2xNi+++xO for the entire range 0≤x<0.5 are reported. For values ofx≤0.3, the lattice appears to be antiferromagnetic and is cubic above the Curie temperature. For the range of compositions 0.3<x<0.5, the lattice is rhombohedral and apparently ferrimagnetic, a maximum magnetic moment per gram of 31 cgs cm3/g being observed atx=0.46. A maximum ferrimagnetic Curie temperature of 241°K was observed for the compositionx=0.41. These properties are interpreted in terms of a partial ordering of Li and Ni ions into alternate sets of (111) planes which couple antiparallel to one another, the moments within any set being either ferromagnetically coupled or paramagnetic, depending upon the number of nonmagnetic near neighbors in the neighboring planes.

ISSN:0021-8979    

DOI:10.1063/1.1723144

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Quenched zinc ferrite is ferrimagnetic, annealed ferrite paramagnetic at 300°K. Although annealed zinc ferrite has a lambda‐type heat capacity transition at about 9.5°K, quenched zinc ferrite retains only elementary vestigia of this transition. A similar effect exists in Li0.05Zn0.90Fe2.05O4in which the transition temperature is slightly lowered relative to that of zinc ferrite. This temperature shift does not appear to exist for Ni0.1Zn0.9Fe2O4. The magnetic entropy at 300°K is essentially unaltered by lithium substitution or thermal history.

ISSN:0021-8979    

DOI:10.1063/1.1723145

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

In order to study the magnetic interaction between the eightfold and the combined six‐ and fourfold sites in the garnet structure, several germanate garnets have been synthesized. If no magnetic cation is present in the fourfold site no spontaneous magnetization has been found in the temperature range 90° to 500°K. A partial substitution of the nonmagnetic cation in the fourfold site by magnetic cations, however, leads to a spontaneous magnetization.

ISSN:0021-8979    

DOI:10.1063/1.1723146

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The system LaMn1−xNixO3+&lgr;has been prepared under varying conditions for the entire range of compositions 0≤x≤1. The saturation magnetization, lattice parameters, and chemical analysis have been measured for each sample. The origin of discrepancies in the literature on the crystal structure of LaMnO3is shown to be due to different preparation procedures which result in the presence of differing amounts of Mn4+: the lattice symmetry changes from orthorhombic to rhombohedral as the Mn4+concentration exceeds 21% of the total manganese. The system is ferromagnetic with magnetization only slightly less than the spin‐only value over the compositional range 0.2≤x≤0.5: a ferromagnetic Ni3+&sngbnd;Mn3+interaction is indicated. The system remains orthorhombic throughout the range 0≤x<0.5; it shows an increasing distortion to an apparently monoclinic symmetry in the range 0.5<x≤0.8. LaNiO3is rhombohedral at room temperature. The lattice symmetry is compatible with Ni3+in a low‐spin state: this is also in accord with the magnetization values. Qualitative concepts used to interpret the system (La,Ca)MnO3are applied to interpret the magnetic and crystallographic properties of this system as well as the magnetic properties of some rhombohedral perovskite‐type systems rich in Mn3+ions.

ISSN:0021-8979    

DOI:10.1063/1.1723147

出版商:AIP    

年代:1958

数据来源: AIP