Materials Science and Engineering

Biography

Biography: Gaspare Varvaro

Abstract

The demand for digital storage devices is continuously growing in response to the extraordinary increase of the volume of data created worldwide, which would reach the value of 40 zettabytes in 2020. Among the different storage devices currently available, the hard disk drive (HDD), based on the magnetic recording technology, remains the most convenient (cost/GB 0.02 $) and diffusive devise (~400 millions of units sold in 2016) for massive digital data storage. Currently available HDDs using CoCrPt:SiO₂ granular thin films with perpendicular magnetic anisotropy are reaching their physical limit (~1 Tbit/in² recording density) due to thermal fluctuations that hinder a further reduction of in-plane grain size (to 4–5 nm) needed to scale down the bit size. L1₀-FePtX alloy is currently considered the most promising candidate for future recording media with areal densities above 1 Tbit/in² thanks to its high magneto-crystalline anisotropy, which enables it to be thermally stable even at grain sizes down to 3 nm. However, its huge anisotropy implies an increase of the switching field, which cannot be afforded by current available write heads. The writability and thermal stability requirements can be simultaneously addressed by using exchange coupled composite systems, combining two or multiphase magnetic hard and soft materials, where the hard phase provides thermal stability and the soft phase reduces the switching field. An alternative approach involves the use of so-called bit patterned media, which consist of an ordered two-dimensional array of individual magnetic nanostructures with perpendicular anisotropy, each of them representing one bit of information, obtained by nanolithography and/or self-assembly techniques. This communication reports on the fabrication and physical properties of FePtX-based thin films and nanoparticles of potential interest for next generation recording media based on exchange coupled composite materials and bit patterned magnetic recording technology.

Recent Publications:

1.Varvaro G, Casoli F Eds (2016) Ultra-high-density magnetic recording: Storage materials and media designs. Pan Stanford Publishing.

2.Barucca G, Speliotis Th, Giannopoulos G, Niarchos D, Rutkowski B, Czyrska-Filemonowicz A, Agostinelli E, Laureti S, Testa A M, Varvaro G (2017) Magnetic anisotropy phase-graded A1/L10-FePt films on amorphous glass substrates. Mat. Design 123: 147.

3.Varvaro G, Laureti S, Fiorani D (2014) L10 FePt-based thin films for future perpendicular magnetic recording media. JMMM 368: 415.

4.Faustini M, Capobianchi A, Varvaro G, Grosso D (2012) highly controlled dip-coating deposition of fct FePt nanoparticles from layered salt precursor into nanostructured thin films: An easy way to tune magnetic and optical properties. Chem. Mater. 24: 1072.