Chiral magnetoacoustics

Nonreciprocal microwave devices are key components of communication platforms. Nonreciprocity can arise in chiral systems, where chirality refers to a fixed handedness that is preserved under time reversal. Chiral excitations (quasiparticles) provide opportunities for the realization of miniaturized microwave components with directional properties. In particular, surface acoustic waves that propagate in magnetic media are chiral and can display pronounced nonreciprocal character. Because surface acoustic waves are an established technological platform, hybrid surface acoustic wave/spin wave devices have great application potential. In this mini-review, we introduce the general concept of chiral and nonreciprocal magnetoacoustic waves. We discuss a widely employed phenomenological model based on magnetoelastic coupling and magneto-rotation that quantitatively accounts for many experimental findings and give a brief overview over selected experiments and advances in this emerging research field

Magnetic properties of Co/Ni-based multilayers with Pd and Pt insertion layers

In this study, the influence of Pd and Pt insertion layers in Co/Ni multilayers (MLs) on their magnetic properties, e.g. magnetic anisotropies, saturation magnetization, coercivity, magnetic domain size, and Curie temperature, is investigated. We compare three series of [Co/Ni/X]N ML systems (X = Pd, Pt, no insertion layer), varying the individual Co layer thickness as well as the repetition number N. All three systems behave very similarly for the different Co layer thicknesses. For all systems, a maximum effective magnetic anisotropy was achieved for MLs with a Co layer thickness between 0.15 nm and 0.25 nm. The transition from an out-of-plane to an in-plane system occurs at about 0.4 nm of Co. While [Co(0.2 nm)/Ni(0.4 nm)]N MLs change their preferred easy magnetization axis from out-of-plane to in-plane after 6 bilayer repetitions, insertion of Pd and Pt results in an extension of this transition beyond 15 repetitions. The maximum effective magnetic anisotropy was more than doubled from 105 kJ/m3 for [Co/Ni]3 to 275 and 186 kJ/m3 for Pt and Pd, respectively. Furthermore, the insertion layers strongly reduce the initial saturation magnetization of 1100 kA/m of Co/Ni MLs and lower the Curie temperature from 720 to around 500

Trapping ultracold atoms at 100 nm from a chip surface in a 0.7-micrometer-period magnetic lattice

We report the trapping of ultracold 87Rb atoms in a 0.7 micron-period 2D triangular magnetic lattice on an atom chip. The magnetic lattice is created by a lithographically patterned magnetic Co/Pd multilayer film plus bias fields. Rubidium atoms in the F=1, mF=-1 low-field seeking state are trapped at estimated distances down to about 100 nm from the chip surface and with calculated mean trapping frequencies as high as 800 kHz. The measured lifetimes of the atoms trapped in the magnetic lattice are in the range 0.4 - 1.7 ms, depending on distance from the chip surface. Model calculations suggest the trap lifetimes are currently limited mainly by losses due to surface-induced thermal evaporation following loading of the atoms from the Z-wire trap into the very tight magnetic lattice traps, rather than by fundamental loss processes such as surface interactions, three-body recombination or spin flips due to Johnson magnetic noise. The trapping of atoms in a 0.7 micrometer-period magnetic lattice represents a significant step towards using magnetic lattices for quantum tunneling experiments and to simulate condensed matter and many-body phenomena in nontrivial lattice geometries.Comment: 11 pages, 7 figure

Nonreciprocal transmission of magnetoacoustic waves in compensated synthetic antiferromagnets

We investigate the interaction between surface acoustic waves (SAWs) and spin waves (SWs) in a Pt/Co(2nm)/Ru(0.85nm)/Co(2nm)/Pt compensated synthetic antiferromagnet (SAF) composed of two ferromagnetic layers with equal thicknesses separated by a thin nonmagnetic Ru spacer layer. Because of the combined presence of interlayer dipolar coupling fields and interfacial Dzyaloshinskii–Moriya interaction (iDMI), the optical SW mode shows a large nondegenerate dispersion relation for counter-propagating SWs. Due to resonant SAW-SW interaction, we observe a nonreciprocal SAW transmission in the prepared piezoelectric/SAF hybrid device. We demonstrate that the nonreciprocity of the SAW transmission in symmetric SAFs with equal thicknesses of the magnetic layers can show a substantially different characteristic behavior in comparison to asymmetric SAFs or magnetic single layers with iDMI. For the prepared SAF, the nonreciprocal shift of the magnetoacoustic resonance fields and the magnetoacoustic SW excitation efficiency depend on the external magnetic field sweep direction. For one magnetic field sweep direction and angle of the magnetic field, the resonance fields of the waves propagating in one direction are larger than for the waves propagating in the opposite direction. In addition, the magnitude of the nonreciprocal field shift is at minimum if the external magnetic field is aligned perpendicular to the SW propagation direction. The experimental results are in agreement with a phenomenological SAW-SW interaction model

Nonreciprocal magnetoacoustic waves in synthetic antiferromagnets with Dzyaloshinskii-Moriya interaction

The interaction between surface acoustic waves (SAWs) and spin waves (SWs) in a piezoelectric/magnetic thin film heterostructure yields potential for the realization of novel microwave devices and applications in magnonics. In the present work, we investigate the SAW-SW interaction in a Pt/Co(2nm)/Ru(0.85nm)/Co(4nm)/Pt synthetic antiferromagnet (SAF) composed of two ferromagnetic layers with different thicknesses separated by a thin nonmagnetic Ru spacer layer. Because of the combined presence of interfacial Dzyaloshinskii–Moriya interaction (iDMI) and interlayer dipolar coupling fields, the optical SW mode shows a large nondegenerate dispersion relation for oppositely propagating SWs. Due to SAW-SW interaction, we observe nonreciprocal SAW transmission in the piezoelectric/SAF hybrid device. The equilibrium magnetization directions of both Co layers are manipulated by an external magnetic field to set a ferromagnetic, canted, or antiferromagnetic configuration. This has a strong impact on the SW dispersion, its nonreciprocity, and SAW-SW interaction. The experimental results are in agreement with a phenomenological SAW-SW interaction model, which considers the interlayer exchange coupling, iDMI, and interlayer dipolar coupling fields of the SWs

Comparison of omeprazole, metronidazole and clarithromycin with omeprazole/amoxicillin dual-therapy for the cure of Helicobacter pylori infection

In this randomized, multicenter trial, we evaluated the effectiveness and side effect profile of a modified omeprazole-based triple therapy to cure Helicobacter pylori infection. The control group consisted of patients treated with standard dual therapy comprising omeprazole and amoxicillin. One hundred and fifty-seven H. pylori infected patients with duodenal ulcers were randomly assigned to receive either a combination of omeprazole 10 mg, clarithromycin 250 mg and metronidazole 400 mg (OCM) given three times daily for 10 days (n = 81),or a combination of omeprazole 20 mg and amoxicillin 1 g (OA) given twice daily for 14 days (n = 76). Prior to treatment and after 2 and 6 weeks, gastric biopsies from the antrum and corpus were obtained for histology and H. pylori culture. H. pylori infection was cured in 97.4% after OCM and in 65.8% after OA in the per-protocol analysis (p < 0.001) (intention-to-treat analysis: 93.4% and 63.2%, respectively). H. pylori was successfully cultured in 122 patients (77%). The overall rate of metronidazole resistance was 19.7% (24/122), no primary resistance to clarithromycin or amoxicillin was found. In the OCM group, all patients infected with metronidazole-sensitive H. pylori strains (n = 51) and those infected with strains of unknown susceptibility to metronidazole (n = 14)were cured (100%), while 77% (10/13) of those harboring metronidazole-resistant. strains were cured of the infection (p = 0.36). Side effects leading to premature termination of treatment occurred in 2.5% of the patients in the OCM group and in 1.4 % of the OA group. We conclude that combined treatment with omeprazole, clarithromycin and a higher dose of metronidazole is highly effective in curing H, pylori infection, Helicobacter pylori omeprazole and that this regimen remains very effective in the presence of metronidazole resistant strains

Lohnarbeit in der sächsischen Landwirtschaft

Die Studie informiert über die Gesamtsituation des Lohnarbeitssektors, seine bisherige und zukünftige Entwicklung und seine Bedeutung für die sächsische Landwirtschaft. Die umfangreiche Materialsammlung enthält darüber hinaus einen Vergleich zur Entwicklung in Deutschland und eine Stärken-Schwächen-Analyse