摘要:

An investigation of the “frequency effect” has been made for several nickel ferrous ferrites ([Nix2+ Fe1−x2+ Fe23+]O4, 0.28 ≤ x ≤ 1) by making torque measurements for magnetocrystalline anisotropy on the same arc‐image furnace crystals that were used in the microwave work reported earlier. A plot of &Dgr;k1(k1(torque)‐k1(microwave)) versus the mole fraction of Fe2+shows a curve with maximum occuring for low Fe2+at 170°K. This maximum gradually shifts to higher Fe2+until the variation approaches linearity at 77°K. The &Dgr;k1for these crystals in the temperature range77°K ≤ T ≤ 300°Kare in relatively good agreement with those calculated from Clogston's slow relaxation theory. The calculated relaxation time (&tgr;) was plotted as a function of the mole fraction of Fe2+for several temperatures between 170°K and 77°K. This shows that higher Fe2+yields a lower temperature at which the relaxation process begins and is consistent with the observed &Dgr;k1vs. Fe2+curves.

ISSN:0094-243X    

DOI:10.1063/1.2953912

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

The introduction of small amounts of iodine in ferrimagnetic single crystals causes an extensive modification of the magnetic properties. We observe from microwave measurements made on crystal spheres at temperatures between 80°K and 300°K a large reduction both in the resonance field and in the ferrimagnetic anisotropy energy. Thus forNiFe2O4and for YIG, −K1/Ms at 80°K decreases from 340 to 12 Oe and from 45 to 15 Oe, respectively. The large reduction of anisotropy can be explained on the basis of a single ion anisotropy model. The new properties (very weak magnetic anisotropy and low resonance field) are very favourable for microwave ferrite devices.

ISSN:0094-243X    

DOI:10.1063/1.2953913

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Linewidth measurements from 77–300°K and room temperature off‐resonance effective linewidth data at 9 GHz show that the microwave losses in ultra‐low‐loss Ca&sngbnd;V&sngbnd;In substituted YIG and Ca‐Ge‐In‐YIG are completely resolvable in terms of known processes and that only a small part of the loss is due to anisotropy broadening. For the lowest linewidth of 2 Oe observed to date (Ca‐Ge‐In‐YG), about 0. 5 Oe is due to rare earth impurities 0. 9 Oe is from porosity broadening, and 0. 2 Oe is from anisotropy. The remaining 0.4 Oe contribution is comparable to expected “intrinsic” single crystal linewidths.

ISSN:0094-243X    

DOI:10.1063/1.2953914

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

To clarify the conditions for generation of amplified Hahn‐type echoes in ferrimagnets, experiments were conducted with composite samples formed by imbedding single crystal YIG wafers at various positions at and near the end of a poly crystalline YIG bar of similar cross section and 4&pgr;M value. The poly crystalline component provided the internal field and field gradient needed for echo formation but did not contribute directly to the signal because of its broad linewidth. As the single crystal wafer was moved along the magnetic axis of the sample the effects of internal field, field gradient, and microwave coupling on the echo were studied. The results determine the effective volume of the sample producing the echo, indicate thatthis volume is diminished by nonuniformities in the surface demagnetizing field, and show that an axial gradient on the order of 300 Oe/mm is needed for good echo formation and amplification.

ISSN:0094-243X    

DOI:10.1063/1.2953915

出版商:AIP    

年代:1972

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/v5.frontmatter

出版商:AIP    

年代:1972

数据来源: AIP