Investigation of wear resistance and lifetime of diamond-like carbon (DLC) coated glass disk in flying height measurement process

Flying height has been greatly reduced to less than 10 nm to achieve high-density magnetic storage. This leads to significant disk wear especially, glass disks used in flying height measurement process. This paper reports the utilization of diamond-like carbon (DLC) overcoat to increase the wear resistance and lifetime of commercial glass disks in a flying height tester. Wear resistance of the DLC coated glass disks was investigated in wear test using a triboindentor. The results showed significant wear resistance improvement of the coated disk where the wear depth reduced from 62.2 nm on an uncoated disk to 5–7 nm on 15-nm thick DLC coated disks. Furthermore, lifetime measurement of the coated disk has been performed in a flying height tester. As a result, lifetime of the coated disk has been drastically improved by more than 30 times in comparison to an uncoated disk.     

Design of a low‐cost 1‐20 GHz magnetic near‐field probe with FR‐4 printed circuit board

An ultra‐wideband magnetic near‐field probe based on a conventional low‐cost four layers of FR‐4 printed circuit board is proposed in this article. It can be used to measure the magnetic near‐field strength from RF magnetic sources or electronic devices for EMI conformance test. The operating frequency of the probe is from 1 GHz up to 20 GHz. The probe is constructed based on a coplanar waveguide and stripline with a short‐end loop. The probe dimension is 10 mm × 25 mm × 0.6 mm. The prototype probe is electric field‐shield structure and has a very high unwanted electric field suppression ratio about 17.7 dB. The probe calibration factor from the simulation agrees well with the calibration factor computed from the measurement. The average probe factor is 38.8 dBS/m and probe sensitivity is 47.4 dB μ A/m.