Effects of mechanical contact stress on magnetic properties of ferromagnetic film

Abstract

Mechanical and magnetic degradation of ferromagnetic films under contact stress was systematically investigated through novel experiments and analytical simulations. Permalloy (Ni80Fe20) film was deposited onto silicon substrate, and two different thicknesses of permalloy film (50 nm for sample A and 300 nm for sample B) were examined in this study. Magnetic properties were obtained from B-H loop tracer hysteresis measurement, while the mechanical properties (i.e., hardness and elastic modulus) were measured using nanoindentation techniques. It was observed that the 50 nm thick permalloy film showed weaker magnetic strength (lower coercivity and saturation magnetic flux values) and lower hardness than the 300 nm thick permalloy film. To apply mechanical contact stress on the permalloy film samples, nanoscratch experiments were performed using ramp and constant loading scratch profiles. Then, the resulting mechanical degradation (surface physical damage) of the two samples was determined from atomic force microscope measurements, and the corresponding magnetic degradation was analyzed using magnetic force microscope measurements. It was found that the magnetic degradation was more sensitive to the applied contact stress than the mechanical degradation. Comparing the two permalloy film samples, it was observed that the 50 nm thick permalloy film showed more magnetic degradation under the same contact stress, which could be attributed to its lower material strength.

Quantitative relationship between contact stress and magnetic signal strength in perpendicular recording media

“…Since this scratching velocity was very low, the frictional heat effect could be neglected. [3][4][5] Also, the applied normal load for scratching the PMR samples ranged from 80 to 600 lN. The stress induced by the applied normal load during the nanoscratch experiments is comparable with that induced by slider-disk contacts.…”

“…Furukawa et al 3,4 revealed that the scratch-induced demagnetization in PMR disks was mainly caused by plastic deformation, which results in magnetic grain tilt. Moreover, Lee et al 5 investigated the plastic yield and magnetic degradation of ferromagnetic films under contact stress by the means of nanoscratch experiments and analytical simulations. Their results showed that the magnetic degradation was more susceptible to the applied contact stress than the plastic yield.…”

Investigating atomic structure of thin carbon film under mechanical stress and frictional heat generation

“…To get more physical understanding on the difference of the nanoscratch depth with the burnishing level, the in situ contact stress during the nanoscratch test was estimated using the Hamilton's sliding contact model [30,31]. Table 1 shows the material properties of the scratch tip and the head slider that were used in the numerical simulation.…”

Three-layered sandwich structured carbon film prepared by sputtering and ion/electron/ion alternative irradiation

“…Wang et al prepared electron irradiated monolithic carbon film by electron cyclotron resonance (ECR) sputtering technique, which has been proved to have relatively high conductivity [4] and paramagnetism [5]. However, it was also found that this kind of film had the limitations of relatively low wear resistance, hardness and poor bonding strength with substrate, which means that it would suffer a higher risk in deformation, spalling and abrasion when facing a contact or friction in MEMS, leading to a change in conductive property [6] or magnetic degradation [7]. In order to improve the tribological and mechanical properties of the electron irradiated film, we constructed a three-layer sandwich structured carbon film by using multilayer coating technique and assembling the electron irradiated film with relatively hard ion irradiated carbon film together.…”