Tomomi Funayama

The applicability of CPP-GMR heads for magnetic recording

In this paper, we mainly discuss the extendability of current perpendicular to plane giant magnetoresistive (CPP-GMR) heads beyond 100 Gbpsi by using micromagnetic simulation and simulation techniques. An area map of CPP-GMRs resistance-area product (RA) and magnetoresistive ratio for several areal densities is made, which suggests that downsizing of a CPP-GMR head does not cause a decrease in output voltage differently from a current in plane GMR (CIP-GMR) head. At this point, a CPP-GMR has the advantage of extendability to a higher areal density over CIP-GMR, and is the major candidate for the next generation. A CIP-GMR seems to have a scalability limit around 100-200 Gbpsi. On the other hand, the area map also suggests that the RA of the CPP-GMR is a more important keyfactor for higher areal density than for CIP-GMR. The CPP-GMR, therefore, requires not only higher MR, but also less RA as areal density gets higher. Tunneling MR (TMR) has exactly the same problem, so CPP-GMR also has many advantages over TMR, with too high an RA. Additionally, we present CPP-GMR films with the potential for around 500 Gbpsi and discuss a suitable read-head structure for CPP-GMR. Micromagnetic simulation results indicate that the read track width will be controlled by a magnetic field due to the sense current of CPP. We will discuss overall studies on scalability of CPP-GMR.

Mn substitution effect on magnetostriction temperature dependence in Tb0.3Dy0.7Fe2

Magnetostriction temperature dependencies in Tb0.3Dy0.7 (Fe1−xMnx)2 were investigated. Mn substitution lowers the spin reorientation temperature, at which magnetostriction shows a sharp drop. Moreover, Mn containing compounds show larger magnetostriction than that for a Mn‐free compound at low temperature. Mossbauer measurements show that easy magnetization direction for the Mn containing compound is in the 〈111〉 direction at 300 K, while it is in the 〈100〉 at 77 K. These results indicate that the tetragonal distortion λ100 increases by Mn addition in Tb0.3Dy0.7Fe2.

Magnetic properties and magnetostriction in grain‐oriented (TbxDy1−x)(Fe1−yMny)1.95 compounds

The magnetic properties and magnetostriction in grain‐oriented (TbxDy1−x)(Fe1−yMny)1.95 compounds with 0.3≤x≤0.5, 0≤y≤0.2 prepared by the Bridgman method have been investigated. It is confirmed that the Mn substitution not only lowers the spin reorientation temperature but also enhances λ〈100〉. This large λ〈100〉 is contradictory to the single‐ion model. For Tb0.5Dy0.5 (Fe0.9Mn0.1)1.95 compound, no spin reorientation, which induces the sharp drop in the magnetostriction is seen in the temperature range from 77 to 400 K. In addition, by choosing the appropriate compressive stress, the quite excellent thermal stability and the large magnetostriction of 2000 ppm in the low applied field can be realized in the Tb0.5Dy0.5 (Fe0.9Mn0.1)1.95 compound. These features make Tb0.5Dy0.5 (Fe0.9Mn0.1)1.95 a promising material applicable to the various giant magnetostrictive actuators.

Thermal management design for GMR head ESD-robustness

The effect of spin valve (SV) resistance, SV/lead contact resistance, heat conductance and heat capacitance of SV, and the blocking temperature of antiferromagnetic (AF) material in the SV on electrostatic discharge (ESD)-voltage was studied with test-elements in which the lead structure and the AF film were varied. Reducing SV/lead contact resistance by means of using lead-overlaid structure showed the largest effect on ESD-robustness among those factors.

Magnetoelastic properties of Gd(Fe1−xCox)2 and Dy(Fe1−xCox)2

Abstract The anisotropic magnetostrictions of the cubic Laves phase compounds Gd(Fe1−xCox)2 and Dy(Fe1−xCox)2 pseudobinary system have been measured from 8 to 130 K below their ordering temperatures. The concentration dependence of anisotropic magnetostriction for these two systems has been observed. An attempt is made to find the reason for the high magnetostriction in DyCo2 and GdCo2. The results obtained suggest that the high anisotropic magnetostriction of RCo2 (R:Gd, Dy) relates to the strong magnetocrystalline anisotropy caused by cobalt.

Co Substitution Effect on Magnetic and Magnetostrictive Properties of DyFe 2

The Co substitution effect on the magnetostrictive properties of DyFe2 has been investigated using magnetic measurement. The specific saturation magnetization σs of the Dy(Fe1-xCox)2 compounds firstly decreases with x and then increases. The magnetostriction constant λt of these compounds increases with x monotonically. These phenomena are been discussed.

Mössbauer study on the pseudobinary Dy (Fe1−x Co x )2 compound with [100] easy direction

In order to research the high magnetostriction effect of some rare-earth transition metal intermetallic compounds such as the RFe2 or RCo2, systems, we have investigated microscopically the physical properties of Dy(Fe1−xCox)2 by Mössbauer spectroscopy. Hyperfine field(Bbf), quadrupole splitting(Q.S.) and isomer shift(I.S.) in the Dy(Fe1−xCox)2 system have been measured at room temperature and 78 K. The easy axis of magnetization lies along the [100] axis. Especially we have found the close correlation between Q.S. and magnetostriction, that is the Q.S. for Dy(Fe1−xCox)2 increase in the Co rich region where the magnetostriction become large at 78 K.

MR enhancement of CPP-GMR by CCP-NOL spacer and Fe/sub 50/Co/sub 50/ magnetic layers

This paper reports that further increase of magnetoresistance (MR) ratio to 6.5/spl sim/8.5% is achieved by using Fe/sub 50/Co/sub 50/ magnetic layers, in addition to current-confined-path(CCP)-nanooxide layer(NOL). The CCP-CPP structure is composed of Ta/Ru/PtMn/Co/sub 90/Fe/sub 10//Ru/pinned layer/NOL spacer/free layer/Cu/Ta cap. Using Fe/sub 50/Co/sub 50//Cu as pinned and free layers, an MR ratio of 6.5/spl sim/8.5% is obtained at area resistance (RA)=300/spl sim/1000 m/spl Omega//spl mu/m/sup 2/ and if Co/sub 90/Fe/sub 10/ is used, MR ratio of 3/spl sim/4% is shown at RA/spl sim/300 m/spl Omega//spl mu/m/sup 2/. The increase of MR ratio is explained by increase of spin dependent scattering at the interface of Fe/sub 50/Co/sub 50/ and Cu metal path where current is concentrated. Conduction examination shows that there is a resistance increased caused by joule heating effect with increasing voltage, indicating that great majority of current flows in metal paths. The origin of MR comes from nano-constricted metal path regions which dimension is less than the mean free path of electron.

The applicability of CPP-GMR for over 100 Gbpsi

Summary form only given. CIP-GMR (Current In-Plane GMR) film with 15-20% MR ratio could be applied to around 100 Gbpsi but it seems there are no major candidates for recording density over 100 Gbpsi. Now the most probable candidate i.e. the TMR (tunneling MR) head seems doubtful in terms of scalability toward the over 100 Gbpsi region because of its much higher resistance than CIP-GMR heads. We discuss the applicability of CPP-GMR (Current Perpendicular to Plane GMR), which is another candidate, for over 100 Gbpsi with simulation results and some experiment results.