Temperature Dependence Of Magnetic Resonance Research Articles

Temperature dependence of magnetic resonance in ferrimagnetic GdFeCo alloys

We provide a macroscopic theory and experimental results for magnetic resonances of antiferromagnetically-coupled ferrimagnets. Our theory, which interpolates the dynamics of antiferromagnets and ferromagnets smoothly, can describe ferrimagnetic resonances across the angular momentum compensation point. We also present experimental results for spin-torque induced ferrimagnetic resonance at several temperatures. The spectral analysis based on our theory reveals that the Gilbert damping parameter, which has been considered to be strongly temperature dependent, is insensitive to temperature. We envision that our work will facilitate further investigation of ferrimagnetic dynamics by providing a theoretical framework suitable for a broad range of temperatures.

Temperature Dependence of the Nitrogen-Vacancy Magnetic Resonance in Diamond

The temperature dependence of the magnetic-resonance spectra of nitrogen-vacancy (NV-) ensembles in the range of 280-330 K was studied. Four samples prepared under different conditions were analyzed with NV- concentrations ranging from 10 ppb to 15 ppm. For all samples, the axial zero-field splitting (ZFS) parameter D was found to vary significantly with temperature, T, as dD/dT=-74.2(7) kHz/K. The transverse ZFS parameter E was nonzero (between 4 and 11 MHz) in all samples, and exhibited a temperature dependence of dE/(EdT)=-1.4(3)x10{-4} K-1. The results might be accounted for by considering local thermal expansion. The temperature dependence of the ZFS parameters presents a significant challenge for diamond magnetometers and may ultimately limit their bandwidth and sensitivity.

Temperature dependence of magnetic resonance in NiO nanoparticles

Magnetic resonance measurements of different size NiO nanoparticles were performed at frequencies below 33 cm−1 and in the temperature range 300–500 K. The samples were earlier investigated by superconducting quantum interference device magnetometry and electron spin resonance spectrometry. The spectra were scanned by changing the sample temperature at fixed frequencies. At room temperature, resonance frequency for bulk NiO is 36.5 cm−1. At higher temperatures, the magnetic resonance frequency becomes lower, and at the Néel temperature goes to zero. For the 435 Å nanoparticles, we detected only one resonance peak. Extrapolation of the dependence to zero frequency gives a Néel temperature of 492 K. For 57 Å NiO, we observed two different peaks. One of them was at the same place as for 435 Å NiO, and another one was at higher temperatures. There exists several mechanisms which determine the magnetic structure of NiO nanoparticles, and, respectively, its resonance spectra. We believe that the magnetic resonance in 435 Å NiO corresponds to a bulklike structure, and the detection of two separate peaks in 57 Å NiO by a “size effect,” which is consistent with a many-sublattice magnetic structure and corresponding additional exchange modes of magnetic resonance.

Anomalous frequency dependence of spin relaxation in the concentrated spin glass, a − (Fe 0.16Ni 0.84) 75P 16B 6Aℓ 3

Systematic studies of the frequency and temperature dependence of magnetic resonance in the most concentrated spin glass studied so far, a − (Fe 0.16Ni 0.84) 75P 16B 6Aℓ 3, show the low T linewidth rise observed previously in randomized spin systems. The parameter describing this rise not only has the resonant anomaly seen earlier in other concentrated spin glasses but also exhibits a dramatic increase below 3.5 GHz. The results are not adequately explained by any existing model.