Landau-Lifshitz-Gilbert (LLG) micromagnetic recording field analysis of a single-pole-type (SPT) head using a parallelized program with a PC cluster system is investigated. The use of a PC cluster system allows dynamic calculations of SPT write head models with cells 10 nm a side. An 8-CPU system realized a calculation speed 30 times faster than the original program, which used a 64-bit single processor system. The dc and dynamic recording fields are investigated for various pole tip structures and material characteristics. First, the dc (quasi-static) recording fields are compared for LLG and FEM calculations. Next, it is shown that an optimum non-zero throat height exists that maximizes recording field strength. The addition of a trailing shield is found to be effective for obtaining a larger recording field gradient. Dynamic recording fields are also derived for various head structures and materials.
Ferromagnetic resonance (FMR) measurements using coplanar waveguides (CPWs) make it possible to perform highly sensitive magnetization measurements, since a CPW can concentrate electromagnetic waves onto a narrow signal line. In this study, we aimed to perform FMR measurements of a minute individual magnet, and investigated the dependence of the sensitivity on the signal line width. We fabricated CPWs on MgO wafers and placed an individual NiFe dot on each of CPWs. NiFe dots with a thickness of 30 nm and various lateral sizes, i.e. 50 × 100, 50 × 80, 50 × 30, 50 × 20, and 50 × 10 μm, were fabricated. The signal line widths of these samples were 150, 100, 50, 30, and 15 μm, respectively. The external magnetic field dependence of the resonance frequency was well fitted by Kittel’s formula. As expected, we obtained larger signals from smaller samples, because narrower signal lines that create larger rf fields were employed for smaller samples.
We propose a new system for sensing the positions of up to five wireless magnetic markers using phase detection. It consists of five resonated markers, a driving coil, and pickup coils. Slim LC resonated markers were fabricated and a detector was formed by connecting high-speed AD converters. The system has a position accuracy of around 1 mm, and can be used for highly accurate position sensing without magnetic shielding, because it is free from earth field noise. We tracked fingertips using five resonated markers.
The authors examined the reduction in the electrical time constant with the aim of achieving high response in a moving magnet linear actuator (LA). This paper describes the relationship between the mover radius, the slot width, and the electrical time constant of the prototype LA. The electrical time constant of the LA can be decreased by 30% by increasing the mover radius from 11 mm to 13 mm and by increasing the permanent magnet thickness from 3 mm to 4 mm. It can also be decreased by 18% by increasing the slot width from 3 mm to 5 mm.