Magnetic anisotropy of textured CrO2 thin films investigated by X-ray magnetic circular dichroism

Highly a-axis-textured CrO₂ films have been deposited on Al₂O₃ (0001) substrates by chemical vapor deposition. CrO₂ has been found to have highly a-axis (010)-oriented columnar growth on a Cr₂O₃ (0001) initial layer. The six-fold surface symmetry of the Cr₂O₃ initial layer leads to three equivalent in-plane orientations of the a-axis-oriented CrO₂ unit cell. We report Cr L_2,3 X-ray magnetic circular dichroism data along the surface normal and at 60° off-normal sample orientation. For a 60° sample alignment, a strong increase of the projected orbital moment could be observed for unoccupied majority t_2g states using moment analysis. Therefore, the c axis is identified as the intrinsic magnetic easy axis of CrO₂. In addition, a small spin moment and a very strong magnetic dipole term T_z have been found. Received: 8 January 2002 / Accepted: 8 January 2002     

Antimagnons in ferrimagnets

Purely antiferromagnetic intrinsic oscillations of magnetic ions in a tetragonal ferrimagnet are considered. The magnetic ions occupy two double positions (forming four magnetic sublattices) so that the center of symmetry for each position is not a closed element. Not involving the total magnetization vector, the oscillations are not excited by the magnetic field; however, the oscillations can be excited by an alternating electric field or by a combination of a constant electric field and the alternating magnetic field of a certain frequency. This phenomenon is a dynamic manifestation of the magnetoelectric interaction. These oscillations, representing a new special type of spin waves (magnons), were called antimagnons. The intrinsic frequencies of antimagnons, as well as the corresponding susceptibilities, were determined. Quantitative estimates were obtained for a Mn₂Sb-based ferrimagnetic phase in both easy-axis and easy-plane orientation states.     

Low-lying states of 6He studied via the 6Li(t,3He)6He reaction

We present the recent experimental results on the ⁶He structure studied by the ⁶Li(t, ³He)⁶He reaction at 336 MeV. Above the conspicuous peaks for ground and first excited states for ⁶He, we have observed a broad structures at E _x∼ 5 MeV, and E _x∼ 15 MeV. The angular distribution of this structure exhibits the dominance of a ΔL = 1 transition, indicating the existence of intruder dipole states at low excitation energies in ⁶He. A slight admixture of positive-parity states in this structure has been indicated as well. Received: 1 May 2001 / Accepted: 4 December 2001     

Jahn-teller chromium ions in CdF<Subscript>2</Subscript> and CaF<Subscript>2</Subscript> crystals: An EPR spectroscopic study in the frequency range 9.3–300 GHz

The bivalent chromium impurity centers in CdF₂ and CaF₂ crystals are investigated using electron paramagnetic resonance (EPR) in the frequency range 9.3–300 GHz. It is found that Cr²⁺ ions in the lattices of these crystals occupy cation positions and form [CrF₄F₄]^6? clusters whose magnetic properties at low temperatures are characterized by orthorhombic symmetry. The parameters of the electron Zeeman and ligand interactions of the Cr²⁺ ion with four fluorine ions in the nearest environment are determined. The initial splittings in the system of spin energy levels of the cluster are measured.     

Synthesis of ladder-type filters based on SAW resonators

A synthesis method for ladder-type filters based on SAW resonators is described. SAW devices are designed with modified equations for coupled waves. Nomograms for choosing the geometry of the filters on ST, X-cut quartz and on 36° Y, X-cut LiTaO₃ substrates are presented. Theoretical results are compared with experimental data.     

Numerical simulation of silane decomposition in an RF plasma

A model of silane decomposition in a radio-frequency argon plasma is constructed. The concentrations of SiH₄ decomposition products, as well as products of synthesis (higher silanes), are calculated. The role of metastable argon atoms in the formation of SiH₃ radicals and the higher silanes is analyzed.     

Individual and center-of-mass resonances in the motional spectrum of an electron cloud in a Penning trap

We have examined experimentally the motional spectrum of an electron cloud confined in a Penning trap. When the axial oscillation is excited by a radio frequency field the resonance exhibits a double structure. Both components depend differently on the number of trapped electrons and have different shape and width. We conclude that one of them corresponds to the excitation of the individual electrons while the other is the center-of-mass mode of the cloud. The threshold behaviour of the center-of-mass resonance suggests that it is a parametric instability of a Mathieu type equation of motion. Received 11 July 2001 and Received in final form 12 November 2001