Glen E. Everett

High Pressure Microwave Cavity for Use in Magnetic Resonance

A sapphire cone terminated at the large end with a metallic sample serves simultaneously as a pressure seal and the resonant structure for a 1‐cm magnetic resonance spectrometer.

Ferromagnetic Resonance with the Magnetic Field in a (111) Plane of a Cubic System

The condition for ferromagnetic resonance with the magnetic field directed at an arbitrary angle in a (111) plane of a cubic system has been calculated. The first‐ and second‐order cubic anisotropy contributions have been included and the results calculated to second order. The second‐order constant K2 contributes to the angular dependence in first order while both K1 and K2 contribute is second order. The second‐order contribution is very important for materials such as EuO which have K1 and K2 of comparable magnitude. We have measured the angular dependence of the ferromagnetic resonance in a (111) plane of EuO at 4.2°K and 25 GHz. The measured amplitude of 4.27 Oe is in good agreement with the calculated value of 4.82 Oe.

Magnetic anisotropy constants of Fe and Ni at 77, 4.2, and 1.09 K: Interdomain configuration transitions in Ni

The magnetocrystalline anisotropy constants of Ni and Fe have been determined at 77, 4.2, and 1.09 K from M⊥(ϑ) measurements above technical saturation. At 4.2 K and below the X2↓ hole band contribution is observed for H↘0 rotation in the (100) and (110) planes. Anisotropy constants, K1, K2, K3, and K4 determined for Ni and K1, K2, and K3 for Fe are compared with previous values from torque measurements. Second‐order interdomain configurations transitions in M∥ versus H have been measured for H↘0 in a (100) plane of Ni. The angular dependence of the transition fields is in good agreement with the theory of Lawton and Stewart extended to include higher‐order contributing anisotropy constants.

Single crystal magnetization studies of DySb

Abstract High resolution magnetization measurements in single crystal-spherical DySb samples have been performed versus T in fields to 23.6 kOe. Measurements with H along principal crystallographic and 〈11 2 〉 directions are interpreted in terms of the intermediate metamagnetic phase having the HoP structure. Magnetization components parallel and perpendicular to the applied field for field rotations in (110) and (111) crystallographic planes have been measured and are interpreted in terms of a simple model with a single critical field. For H ∥ 〈110〉, M and H are collinear. The (M - H - T) phase diagram has been determined for H ∥ 〈110〉. The metamagnetic transition is 1st order below a critical point Pc = (8.5 K, 14.7 kOe) becoming 2nd order above. Field induced order for T >TN is observed in agreement with the results of Brun et al. The absence of hysteresis in M∥(θ) for H in (110) and (111) planes is interpreted as evidence for the tunneling model in DySb.

Tricritical behavior in DySb

Abstract A tricritical point has been observed between two magnetically ordered phases in DySB at 8.5 K and 14.7 kOe. A triple point has been observed at 9.7 K and 12.4 kOe.

Temperature Dependence of the Ferromagnetic Resonance Linewidth of Europium Sulfide

The temperature dependence of the ferromagnetic resonance linewidth of highly polished single‐crystal spheres of EuS was measured in the range from 2.2° to 30°K, using standard microwave techniques at a frequency of 22.65 GHz. The linewidth increases from ∼5 Oe at 2.2°K to ∼400 Oe at the Curie point, and continues to increase in the paramagnetic range to a value of 1000 Oe at 78°K. The linewidth varies linearly with reciprocal magnetization from 2.2° to 18°K, as predicted by the Landau‐Lifshitz equation and can be characterized by a temperature‐independent microphysical damping constant, λ, equal to 1.9±0.09×108 rad/sec within this temperature range.

Experimental search for the first‐order phase transition in Fe with H↘ along a [111] direction

High‐resolution magnetization measurements in Fe single crystal spheres at 4.2 and 1.09 K do not exhibit the predicted first‐order phase transition for H↘=H0[111]. Measurements at 0.1° intervals near the expected [111] direction, analyzed to determine the maximum slope δM/δHi, gave no indication of approach to a critical region. The obervation of the transition in DyAl2 and R‐E iron garnets but not Fe is not presently understood.

Antiferromagnetic resonance in EuTe

From the investigation of the angular dependence of the antiferromagnetic resonance, it is shown that EuTe is an easy plane antiferromagnetic with an in plane anisotropy that is very small (HA, < 10 gauss). The multiple branches are accounted for by assuming domains associated with each of the body diagonals and having approximately equal volumes.

Low temperature magnetic heating in single crystal NiO

Abstract We have observed a latent heat associated with the spin flop phenomena in a NiO single crystal at 2°K. This measurement shows the spin flop field to be less than 600 oe and the inplane anisotropy field to be approximately 0.1 oe.

Temperature Dependence of the Antiferromagnetic Resonance Linewidth in EuTe

The linewidth of EuTe has been measured as a function of temperature through and above the Neel temperature. The samples used were single‐crystal spheres, the magnetic field lying in a (111) plane along a 〈112〉 direction. EuTe is an easy‐plane antiferromagnet having an in‐plane spin‐flop field of 700 G. These measurements at 24 GHz and about 8½ kG were for the low‐frequency branch in the spin‐flopped condition. The temperature dependence of the linewidth is similar to results obtained on other antiferromagnets. The linewidth rises from 150 G at 0.1 TN to a sharp maximum of 2700 G near, but slightly above TN, dropping to 1000 G at 2.0 TN. The results in the paramagnetic region have been compared with the [T/(T−TN)]¾ dependence predicted by Mori and dependence predicted by Mori and Kawasaki. Fitting this expression to the measured linewidth at 77°K gives good agreement down to 12°K (TN=9.6°K). For the antiferromagnetic region, the linewidth decreases approximately linearly with temperature and is not expla...