V. Jaccarino

High temperature EPR linewidths in MnO and MnS

Abstract EPR linewidths ΔH in MnO and MnS were studied at 300–1100°K. The remarkable constancy of χT(ΔH) for T ⪆ 3TN follows from an extension of the Mori-Huber theories and delineates the region where critical-like behavior first becomes apparent as T approaches TN.

New value for the 55Mn nuclear magnetic moment

Abstract The magnetic moment of 55Mn has been determined by ENDOR experiments on Mn2+ in CaWO4, CaO and ZnS. A new value of 55μ=3.4438±0.0020 μn is assigned.

On the rigid lattice dipolar broadening of the Mn2+ EPR in the dilute limit☆

Abstract “Naively” calculated values of the dipolar EPR linewidth of Mn doped CaF 2 and PbF 2 are larger than those observed. This discrepancy is resolved when, in calculating the second and fourth moments, Mn ions with different values of m 55 are considered “unlike” and the contribution of exchange-coupled nearest neighbor ions is omitted.

Temperature dependence of the antiferromagnetic resonance linewidth in MnF2

Abstract The temperature dependent contribution to the antiferromagnetic resonance linewidth in MnF 2 has been measured at K-band frequencies (∼ 23 GHz) between 5° and 40°K. It can be closely approximated by a T 4 power law except at the highest temperatures.

Pb2MnF6: Antiferromagnet and superionic conductor☆

Abstract Measurements of the EPR linewidth versus temperature indicate Pb 2 MnF 6 is an antiferromagnet with T N = 30 ± 1 K. The disappearance of the low-field NMR lines at T N confirms these results. The coalescence of the 19 F NMR lines above 500 K show the anion conductivity to be comparable to PbF 2 .

Field dependent enhancements of the NMR in antiferromagnets

Abstract The strongly field dependent enhancement η of the NMR in antiferromagnets leads to an ( H SF − H 0 ) -1 divergence of η and to the possibility, at some particular value of H 0 , for H rf to be totally screened. The latter effect is demonstrated for the 55 Mn NMR in MnF 2 .

Spatial-frequency correlation in an inhomogeneous line☆

Abstract The variation of T 2 across the main 19 F resonance line in Mn:FeF 2 has been measured and shows strong correlation of the nucleis spatial and frequency positions.

Magnetic resonance lineshapes in exchange coupled paramagnets

Abstract Systematic discrepancies between predicted and observed exchange narrowed EPR and NMR resonance linewidths in MnF 2 , KMnF 3 , RbMnF 3 are examined. A model lineshape based upon the 2nd, 4th and 6th moments is proposed which improves agreement with experiment.

Suhl-Nakamura interaction and inhomogeneous broadening

Abstract The effect of microscopic inhomogeneities on the Suhl-Nakamura indirect interaction between nuclear spins is shown to alter the NMR line shapes in the direction observed experimentally. Two simple models for exploring these effects are proposed.