Ion Irradiation for Planar Patterning of Magnetic Materials

Abstract

Kr+ ion dose dependence of the magnetic properties of MnGa films and the fabrication of planar-patterned MnGa films by the local ion irradiation technique were reviewed. The magnetization and perpendicular anisotropy of the MnGa vanished at an ion dose of 1 × 1014 ions/cm2 due to the phase change of the MnGa from ferromagnetic L10 to paramagnetic A1 phase. The average switching field Hsw of the planar-patterned MnGa increased with decreasing the bit size, implying low bit edge damage in the patterned MnGa, whereas a rather large switching field distribution (SFD) of 25% was confirmed for a bit size of ~40 nm. Time resolved magneto-optical Kerr effect measurements revealed that as-prepared MnGa exhibits an effective anisotropy field Hkeff = 20 kOe, its distribution ΔHkeff = 200 Oe, and Gilbert damping α = 0.008. The ion-irradiated MnGa films exhibited larger Hkeff = 22–23 kOe than that of the MnGa before the ion dose. Thus, ion irradiation does not decrease the perpendicular anisotropy, which suggests a small bit edge in the patterned MnGa. ΔHkeff increased from 0.2 kOe to 3 kOe, whereas the length of disorder in the film ξ decreased from 10 nm to 3 nm by ion irradiation.

Perpendicular Anisotropy and Damping of MBE-grown MgO/Fe/Au(001) and Au/Fe/Au(001) Trilayers

“…Prior to the deposition, MgO substrate was cleaned by Ar + ion bombardment with an acceleration energy of 1 kV followed by annealing at 1000˚C for 2 min. All the layers were deposited at temperature less than 100˚C, and Au (20) under layer was annealed at 400˚C for 30 min to obtain atomically flat Au surface before the deposition of Fe layer. The deposition rate for all layers were fixed at 0.01 nm/s.…”

Challenges toward development of rear‐earth free FeCo based permanent magnet

“…As follows from Equation (3), demagnetizing field H d normally works in the direction to weaken magnetization inside magnetic material (negative direction), the field strength being proportional to M s . In addition, Equations ( 4) and (5) suggest that H d heavily depends on the ellipsoid's aspect ratio k (= D/t). For example, with sheet shapes like rolled plates or sputtered films, demagnetization factor N D in the long axis direction is close to 0, while demagnetization factor N t in the short axis direction is close to 1; therefore, big H d occurs in the thickness direction.…”

“…Many such materials show ferromagnetism when ordered, while being nonmagnetic in disordered state; this property is explored in terms of application to bit patterned media, a new generation of ultra-high density recording media. 5 Regarding Fe 16 N 2 , its giant magnetic moment was reported in 1970s, 6 and then many experiments were carried out; 7,8 recently, formation of single-phase particles was reported, 9 and the compound has been commercialized as a semi-hard material with high M s . Semi-hard properties of this material can be attributed to changes in the crystal structure and band structure due to nitridation of iron.…”

“…Mn‐X magnets are very interesting in that they are composed of nonmagnetic elements; in so doing, H k is often high, and the problem is how to enhance M s . Many such materials show ferromagnetism when ordered, while being nonmagnetic in disordered state; this property is explored in terms of application to bit patterned media, a new generation of ultra‐high density recording media 5 …”

Electropatterning—Contemporary developments for selective particle arrangements employing electrokinetics

“…Laser-based methods have a limited focusing area and a need for high-power sources [23]. A significant limitation in magnetic field-based patterning lies in the requirement of pre-existing magnetic properties [24]. Although many techniques that use electric fields (EFs) rely on photolithographically patterned structures, they provide a series of unique advantages, such as robustness and simplicity, that make them attractive options for electropatterning [25].…”