Experimental Set-Up for Simultaneously Measuring Changes in LD Temperature and Flying Height of HAMR-HGA

Heat-assisted magnetic recording (HAMR) is a promising technology for overcoming the superparamagnetic limit, and thereby enabling the achievement of a recording density beyond 8 Tb/in² in a hard disk drive (HDD) [1]. The HAMR head gimbal assembly (HGA) consists of a HAMR head slider, a suspension, and a laser diode (LD) mounted on the slider. An optical near-field transducer (NFT) and a waveguide are near the write-pole in the head slider. During the writing process, light energy is delivered from the LD to the NFT through the waveguide, and the NFT forms a nano-size thermal spot on the recording medium, thereby reducing its coercivity. Development of an HAMR-HGA requires solving several thermal problems. There are two heat sources. One is the LD, which transforms electrical energy into light energy and heat energy. The heat energy increases the temperature of the LD itself, which reduces the laser power and deforms the slider. The other is the NFT, which absorbs light energy. The absorbed energy is transformed into heat energy. This increases the temperature of the NFT and causes the head to protrude. The thermal deformation and protrusion cause a change in the flying-height (FH). The head thermal protrusion problem has been solved using finite-element method (FEM) simulation [2]. We have developed a novel experimental set-up for measuring the temperature increase and FH change simultaneously.