Magnetic Heads

Abstract

Figure 6.1 shows how rapidly the areal density of hard disk drives (HDD) has been increasing over the past 20 years [1]. Several critical innovations were necessary to bring about such rapid progress in the field of magnetic recording [2]. One of the most significant innovations from the viewpoint of material improvement was the electrodeposition of permalloy (Ni 80 Fe 20 ), which was introduced by IBM in 1979 as the core material of a thin-film inductive head to increase the magnetic recording density [3]. After the introduction of the magneto-resistive (MR) element as the read head and the electrodeposited permalloy as the write head by IBM in 1991 [4], the rate of increase in the recording density of HDDs jumped from 30% per year to 60% per year. Recently, a giant magneto-resistive (GMR) element has been used for the read element instead of the MR element. The rate of increase in the recording density jumped to over 100% per year in 1999, which is an incredible rate of increase. Since 2002, however, the rate of increase has decreased to 30%; thus, new innovations are required to maintain the rate of increase. In 2004, the practical use of perpendicular magnetic recording instead of longitudinal magnetic recording was announced [5]. This system is a critical innovation for developing high-performance HDD systems with high-recording density. The design of the magnetic recording head was changed because of the change of the recording system.The development of a new magnetic recording head with higher performance and smaller dimensions is a key requirement for realizing high-density magnetic recording. Furthermore, to meet the demand for the rapid increase in magnetic recording density, the soft magnetic film in the core must have low magnetostriction, l s , high electrical resistivity, r, high thermal stability, low film stress, and high corrosion resistance, as well as high saturation magnetic flux density, B s . The recording heads, using higher magnetic materials with high value of B s can write to a high-H c

Tuning Side Arm Electronics in Unsymmetrical Cyclotriazadisulfonamide (CADA) Endoplasmic Reticulum (ER) Translocation Inhibitors to Improve their Human Cluster of Differentiation 4 (CD4) Receptor Down-Modulating Potencies

“…Also shown in Scheme 2 is the reaction of o-nitro benzyl tail analog 27 with mercaptoethanol and DBU to give one-armed analog 49 by ipso attack and decomposition of the resulting Meisenheimer complex to SO 2 and 2-(o-nitrophenylthio)ethanol. 35 This compound was mainly of interest for the synthesis of additional unsymmetrical analogs with one benzamide sidearm, as described later.…”