Magnetization reversal in a preferred oriented (111) L1₀FePt grown on a soft magnetic metallic glass for tilted magnetic recording

Abstract

L1(0) FePt is an important material for the fabrication of high density perpendicular recording media, but the ultrahigh coercivity of L1(0) FePt restricts its use. Tilting of the magnetic easy axis and the introduction of a soft magnetic underlayer can solve this problem. However, high temperature processing and the requirement of epitaxial growth conditions for obtaining an L1(0) FePt phase are the main hurdles to be overcome. Here, we introduce a bilayered magnetic structure ((111) L1(0) FePt/glassy Fe(71)Nb(4)Hf(3)Y(2)B(20)/SiO(2)/Si) in which the magnetic easy axis of L1(0) FePt is tilted by ~36° from the film plane and epitaxial growth conditions are not required. The soft magnetic underlayer not only promotes the growth of L1(0) FePt with the preferred orientation but also provides an easy cost-effective micro/nanopatterning of recording bits. A detailed magnetic characterization of the bilayered structure in which the thickness of (111) L1(0) FePt with the soft magnetic Fe(71)Nb(4)Hf(3)Y(2)B(20) glassy underlayer varied from 5 to 60 nm is carried out in an effort to understand the magnetization switching mechanism. The magnetization switching behavior is almost the same for bilayered structures in which FePt layer thickness is >10 nm (greater than the domain wall thickness of FePt). For FePt film ~10 nm thick, magnetization reversal takes place in a very narrow field range. Magnetization reversal first takes place in the soft magnetic underlayer. On further increase in the reverse magnetic field, the domain wall in the soft magnetic layer compresses at the interface of the hard and soft layers. Once the domain wall energy becomes sufficiently large to overcome the nucleation energy of the domain wall in L1(0) FePt, the magnetization of the whole bilayer is reversed. This process takes place quickly because the domain walls in the hard layer do not need to move, and the formation of a narrower domain wall may not be favorable energetically. Our results showed that the present bilayered structure is very promising for the fabrication of tilted bit-patterned magnetic recording media.

Mossbauer study of Thin Films based on FeM (M=Pt or Co)

“…The MMS based on films of the FePt alloy in the Ll 0 phase are very promising for the use in perpendicular magnetic recording, because they have a high uniaxial anisotropy energy (7×10 6 J/ m 3 ) [12,13], which is second only to the energy of more corrosive rare-earth metals [14] and makes it possible to overcome thermal fluctuations and a demagnetizing field, as well as to retain thermal stability of FePt grains even when their sizes reach 5 nm [15]. Furthermore, the FePt films possess a high coercivity [14] and an excellent corrosion resistance [16].…”

“…This makes such materials unsuitable for the use in perpendicular magnetic recording. In recent years, a great number of studies have been aimed at designing and fabricating magnetic multilayer structures based on FePt films which would be suitable for the use in perpendicular magnetic recording (see [12,17,18] and references therein). Despite a large number of publications on the preparation of FePt films for the use in PMR, the design and fabrication of FePt films with the properties required for PMR remain important problems.…”

Structural and Magnetic Properties of MBE Grown (Fe/Pt) (111) Multilayers

“…Presented data can be a starting point both for creating patterned media by local modification of multilayers [2,3] or for creating * corresponding author; e-mail: bacze@ifpan.edu.pl tilted magnetic recording media [4]. Most attention in the literature is being focused on Fe/Pt multilayers and alloys oriented in (001) direction.…”

Suppressed silicide formation in FePt thin films by nitrogen addition

“…The L1 0 ordered phase of FePt alloy is one of the most promising candidates for perpendicular magnetic recording beyond 1 Tbit/in 2 because of its high magnetocrystalline anisotropy constant K u of about 10 7 erg/cm 3 [1] which leads to a high thermal stability against superparamagnetic effects [2]. However, as-deposited films fabricated by sputtering are of the disordered A1 phase.…”