Search

Thermal stability of optical near field transducers is an important issue for heat-assisted magnetic recording (HAMR), which affects HAMR system lifetime. In this paper, dark-field scattering spectroscopy was used to study the stability of nanometer-scaled Au lollipop transducers that were subjected to thermal annealing. Variation in relative peak intensity and red-shifting in peak position can be observed in scattering spectra for transducer after annealing. Based on the optical characterizations on Au thin films and calculations of Mie scattering by finite-difference time domain simulations, the measured changes in transducer scattering properties can reflect annealing-induced variations in optical properties and dimensional feature size for the Au lollipop transducer. Dark-field scattering spectroscopy can be a promising method to examine HAMR near field transducer thermal stability. [ABSTRACT FROM AUTHOR]

In heat assisted magnetic recording (HAMR), optical near field transducer (NFT) is a key component. Au is currently used as NFT material because of its strong surface plasmon effect. Due to the soft property of Au material, reliability of Au NFT becomes a key issue for realizing HAMR production. In this paper, the possibility of alternative materials, including transition metal nitrides (TMNs) and transparent conducting oxides (TCOs) to replace Au is studied. The results show that all of the listed TMN and TCO materials can meet the mechanical requirements at room temperature in terms of hardness and thermal expansion. An optical model, which includes optical waveguide, NFT and FePt media, is used to simulate NFT performances. The results indicate that the resonant wavelengths for NFT with TCO materials are longer than 1500 nm, which is not suitable for HAMR application. TMN materials are suitable for NFT application at wavelength band of around 800 nm. But the NFT efficiency is very low. ZrN is the best material among TMN materials and the efficiency of ZrN NFT is only 13% of the Au NFT's efficiency. Reducing refractive index (n) and increasing extinction coefficient (k) will both lead to efficiency increase. Increasing k contributes more in the efficiency increase, while reducing n has a relatively low NFT absorption. For materials with the same figure of merit, the NFT with larger k material has higher efficiency. Doping materials to increase the material conduction electron density and growing film with larger size grain may be the way to increase k and reduce n. [ABSTRACT FROM AUTHOR]

In this paper, we present a study on two and a half dimensional (2.5D) perpendicular magnetic recording (PMR) media consisting of dual hard magnetic recording layers (RL) with 1st or top RL1 used for conventional data storage and 2nd or bottom RL2 used for dedicated servo with lower linear densities or DC servo patterns with focus on the writability issue of the bottom servo layer (RL2). We demonstrate experimentally the feasibility to magnetically erase, write, and re-write RL2 by laser assist on a home built heat-assisted-magnetic-recording writing test system. Experimental data (by magnetic force microscopy measurements) show that the signal amplitudes of the pre-recorded magnetic patterns for both RL1 and RL2 decrease at almost the same rate with thermal erasure using scanning laser power (Pw) from 13 mW to 23 mW, clearly indicating equally effective laser heating and close temperature rise for RL1 and RL2 for far field laser heating with laser pulse duration in sub-μs and μs range. This is further verified by theoretical simulations of the thermal distribution and the temperature rise depth profile in dual layer media by laser heating. Simulations indicate very little temperature difference of less than 6K (~1% of maximum temperature rise) between RL1 and RL2 because the main mechanism of temperature rises in RL1 and RL2 is due to the effective thermal conduction from the top layers to lower layers. These experimental and theoretical study results could provide useful understanding and insights into servo writing methods of 2.5D PMR media. [ABSTRACT FROM AUTHOR]

Objective: To investigate the correlation between gastric bubble size and laryngopharyngeal reflux pattern in patients with laryngopharyngeal reflux disease(LPRD). Methods: A total of 52 LPRD patients who underwent Dx-pH monitoring and anteroposterior chest radiography at the same time from February 2016 to November 2018 were retrospectively studied. Patients were devided into three position-related groups according to the Ryan score of upright and supine: isolated upright reflux(IUR), isolated supine reflux(ISR) and bipositional reflux(BR) groups. In addition, 13 healthy volunteers with negative pH monitoring were selected as the control group. Gastric bubble size and pH monitoring data among the four groups were compared. SPSS 24.0 was used for statistical analysis. Results: In all the 52 patients, 35 cases (67.3%) were classified as IUR, 9 cases (17.3%) as ISR, and 8 cases (15.4%) as BR. The height of gastric bubbles in the four groups were: IUR (26±14) mm, ISR (9±8) mm, BR (20±13) mm, control (17±15) mm, and statistical difference was found among the four groups( P= 0.004). Post Hoc Multiple Comparisons found that IUR group had statistical difference between ISR group and control group ( P= 0.001, P= 0.034 respectively). There was no statistical difference of gastric bubble width and area among the four groups( P= 0.340, P= 0.186 respectively). The ROC curve of the gastric bubble height with isolated upright and supine reflux patterns was obtained, and the optimal cutoff value of the gastric bubble height was 11 mm. Accordingly, we divided the patiens into two groups with high and low gastric bubble. LPRD reflux pattern distribution was significantly different between the two groups( P< 0.001). The comparison of reflux parameters in pH monitoring also showed that the supine reflux parameters in the lower group were significantly higher than those in the higher group, and the upright reflux parameters in the higher group were significantly higher than those in the lower group( P< 0.001). Conclusions: The height of gastric bubble is significantly correlated with the reflux patterns in LPRD patients. The gastric bubble of patients with IUR is significantly higher than that of patients with ISR. Taking 11 mm as the cutoff value, patients with higher gastric bubble are more prone to upright laryngopharyngeal reflux, while those with lower gastric bubble are more prone to supine laryngopharyngeal reflux.

Objective: To explore the utility of pharyngeal pH monitoring which positive standard is Ryan index in diagnosis of laryngopharyngeal reflux disease. Methods: In a retrospective study, clinical data of 590 patients who had symptoms laryngopharyngeal reflux disease from February 2016 to March 2017 were analyzed. All patients were received electronic laryngoscopy, assessment of reflux symptom index(RSI) and reflux finding score(RFS), and pharyngeal pH monitoring. SPSS 19.0 software was used to analyze the date. Results: There were 94 patients whose Ryan index were positive(15.93%). Among the 94 patients, 70 were positive during upright, 12 during supine and 12 during both upright and supine. There were 40 patients(6.78%)with pH decline events related to symptoms, while those Ryan index were normal. There were 536(90.85%), 417(70.68%), 233(39.49%) and 117(19.83%) patients with pH<6.5, pH<6.0, pH<5.5 and pH<5.0 events respectively. The positive rate of RSI, RFS, RSI and RFS, RSI or RFS were 44.24%, 16.78%, 7.12%, 53.90% respectively. The RFS score in Ryan index positive group was higher than that in Ryan index negative group[(8.2±2.4) vs (4.0±2.9), u =5.424, P <0.05], while the RSI score in Ryan index positive group was not statistically different from that in Ryan index negative group[(11.3±6.2) vs (12.7±5.8), t =1.247, P =0.167]. Conclusions: Pharyngeal pH monitoring is an objective and non-invasive method which can reflect laryngopharyngeal reflux directly. However, with the Ryan index as a criterion for the diagnosis of laryngopharyngeal reflux disease, partial patients may be missed. Further studies are needed to obtain more accurate and objective laryngopharyngeal pH statistical index for diagnosis of laryngopharyngeal reflux disease.