We report a surface electrode trap with a relatively large trap depth (0.6-1.0 eV). The trap electrodes are formed by gold plating an alumina substrate. Calcium ions are trapped approximately 400 µm above the trap surface. We demonstrate micromotion compensation based on parametric resonance for surface electrode traps. Unlike the conventional method based on radio-frequency (rf)-photon correlation in which the wave vector of the laser beam must have a component parallel to the micromotion to be detected, the proposed method is independent of the laser propagation direction. This enables the micromotion component normal to the electrode surface to be detected without increasing the scattered light.

We electroplated Fe-Co-Ni films in ammonium-chloride-based plating baths, and investigated the effect of the Co content on the magnetic properties and the structural ones of the as-plated films. The coercivity increased abruptly when the Co content become more than 60 at.%. As the rough surfaces were observed in the high Co content region, we considered that degradation of the surface is a factor of the abrupt increase in the coercivity. From the XRD analysis, we found that another factor of the abrupt increase is fcc-bcc phase transformation, and concluded that we need to keep the fcc structure to obtain Fe-Co-Ni films with low coercivity.

We electroplated Fe-Ni films in plating baths with ammonium chloride (NH4Cl) and evaluated the magnetic properties of the films. The amount of NH4Cl did not affect the current efficiency of the plating process and the Fe content in the film. The obtained current efficiency of approximately 95% is much higher than our previous study. The coercivity dramatically decreased with increasing NH4Cl from 0 to 15 g/L, and we obtained Fe22Ni78 films with very low coercivity (10 A/m). The Cl -concentration in the plating bath affected the coercivity, and we found that a plating bath with moderate low concentration of Cl -is preferred for obtaining the Fe22Ni78 films with low coercivity.

Effect of an annealing on magnetic properties of Fe-Ni films electroplated in citric-acidbased plating baths AIP Advances 8, 047706 (2018) We have already reported Fe-Ni firms with good soft magnetic properties prepared by using an electroplating method. In our previous studies, we prepared the Fe-Ni films from citric-acid-based baths (CA-baths) and ammonium-chloride-based ones (ACbaths), and confirmed that the coercivity for the AC-baths was lower than that for the CA-baths. In the present study, we investigated reasons for the lower coercivity for the AC-baths to further improve the soft magnetic properties. From an observation of magnetic domains of the Fe 22 Ni 78 films, we found that Fe 22 Ni 78 film for AC-bath had a magnetic anisotropy in the width direction, and also found that the coercivity in the width direction was lower than the longitudinal one for the AC-bath. As an annealing for a stress relaxation in the films reduced the difference in the coercivity, we considered that the anisotropy is attributed to the magneto-elastic effect.

We have already reported Fe-Ni films with good soft magnetic properties prepared by using an electroplating method. In the present study, we employed an annealing for further improvement in soft magnetic properties of the electroplated Fe-Ni films. The annealing reduces the coercivity of the films, and the reduction rate of the coercivity depended on the Cl- ion concentration in the bath. The Fe22Ni78 films prepared in the plating bath with high Cl- ion concentration showed large reduction rate of the coercivity, and we found that the annealing is more effective for high Cl- ion concentration bath since much lower coercivity value can be obtained compared with that for low Cl- ion concentration one.