Perpendicular Recording Media Research Articles

Effects of Ti doping on the magnetic and microstructure properties of the lower magnetic anisotropy CoCrPtRu-oxides layer in a perpendicular recording media

Areal density capacity is constrained by linear and track density, and the recent advancements in magnetic layer structures have led to the development of segmented media. This configuration incorporates a graded magnetic anisotropy layer introduced through a non-magnetic exchange control layer. Optimizing this structural design yielded improvements in the signal-to-noise ratio (SNR) and an elevation in areal density capacity. To comprehensively investigate the magnetic properties and microstructure of the lower magnetocrystalline anisotropy constant (Ku) CoCrPtRu-oxides magnetic capping layer individually, we deposited the (0002) textured magnetic capping layer CoCrPtRu-oxides on (0002) Ru/NiW/NiTa underlayers. Additionally, metallic Ti was introduced into CoCrPtRu targets, replacing half of Ru, resulting in the deposition of the (0002) textured CoCrPtRuTi-oxides film was also deposited and compared to CoCrPtRu-oxides film. A comparative analysis was conducted between the CoCrPtRu-oxides and CoCrPtRuTi-oxides films. Microstructural image mapping and chemical composition analysis revealed that the introduced Ti in core grains diffused to the grain boundaries, enhancing grain separation. This diffusion was facilitated by the more negative formation energy of TiO2 (-3.512 eV/atom) compared with other oxides in the film. Consequently, the CoCrPtRuTi-oxides film exhibited slightly larger grain boundary areas (52%) and smaller grain sizes. Moreover, perpendicular coercivity (243.50 kA/m) and anisotropy were higher. This insight suggests a potential strategy for improving segregation by doping metallic elements, such as Ti, into the core grains, emphasizing the importance of not merely increasing the oxide content (e.g., TiO2).

Structural and magnetic investigations of (1-x) (Bi0.5Na0.5TiO3)0.94-(BaTiO3)0.06 + (x) SrYFe11O19

This paper describes the manufacturing, structural characteristics, and magnetic properties of a ferroelectric (Na0.5 Bi0.5TiO3-BaTiO3; BNBT) and ferromagnetic (SrYFe11O19; SRYFO) composite system. The polycrystalline composite system (1-x) (Bi0.5Na0.5TiO3)0.94-(BaTiO3)0.06 + (x) SrYFe11O19 (x = 0.00, 0.25, 0.50, 0.75 and 1) was synthesized via solid state reaction followed by modified Sol-gel auto-combustion method. Rietveld refinement of the XRD pattern confirms the presence of dual phase symmetry consisting of BNBT (P4bm) and SRYFO (P63/mmc) phases without any external impurity phase. The calculated value of c/a, cell volume, and grain size confirms the lattice distortion. FE-SEM (Field emission scanning electron microscope) was used to study the morphology formation of prepared composites, which revealed that composites are dense ferroelectric grains well distributed in the ferrite matrix, and the grain size of the nanoparticles ranged from 166 to 240 nm. The magnetic characterization was carried out by VSM (Vibrating Sample Magnetometer) with the applied field in the range of −15 kOe to + 15kOe at room temperature. The M−H loop reveals the ferromagnetic nature of composites. The calculated saturation (MS), remnant (Mr), and coercivity (HC) values are increased with ferrite content. The obtained MS/Mr values are found lesser than 0.49, proving the presence of a solitary, non-interacting realm with a single axial anisotropy. These samples can be used to make permanent magnets and perpendicular recording media.

High-resolution alternating magnetic force microscopy using an amorphous FeB-based tip driven by an inverse magnetostrictive effect: Imaging of the high-density magnetic recording media

The improved spatial resolution of the alternating magnetic force microscopy (A-MFM) technique developed in this work is demonstrated using a tip coated with a very thin magnetostrictive Fe-B-based amorphous film. Its magnetization can be periodically reversed using an applied alternating current magnetic field, which leads to alternating mechanical stress at the tip end, thus affecting localized magnetization reversal via an inverse magnetostrictive effect. Spatial resolution improvement is achieved via effective reversible magnetization volume at the sharpened tip end, which promotes a decrease in the total magnetic volume and maintains sufficient sensitivity at a lower coating thickness. A-MFM uses frequency modulation induced by an off-resonant alternating magnetic force between the tip and the sample. Therefore, a magnetic force can be selectively detected near the sample surface, independent of non-magnetic interactions. Due to their smooth surfaces without crystalline grain boundaries, large magnetization, and large magnetostriction compared with those of other magnetic materials, Fe-based amorphous films are suitable for tip coating applications. A 500-kfci perpendicular magnetic recording medium (PMR) was imaged using a 6-nm thick amorphous Fe-B coated tip to produce highly resolved images with minimal detection of the wavelength of the magnetic field of less than 10 nm. Also, 1600-kfci PMR imaging was successfully achieved, with the images showing individual ∼ 15-nm bits.

Scrutiny and correlations of structural, magnetic, and dielectric properties of M-type strontium hexaferrite (SrFe12O19) for permanent magnet applications

Strontium hexaferrite has achieved immense attention in industries, manufacturing crucial components for devices, technological applications, and machine making due to its high coercivity value. The efficient technique of sol–gel auto-combustion was espoused for the synthesis, and the morphological studies affirmed the hexagonal shape of the particles. The magnetic analysis revealed the sample being a potential substance for perpendicular recording media applications. The dielectric studies disclosed relaxations and polarization effects existing in the material. The linkage of structural, magnetic, and dielectric properties and their inter-influences are the remarkable consequences of the research work.

Synthesis, structural, dielectric and magnetic properties of hexagonal ferrites

Neodymium-substituted strontium hexa-ferrites Sr0.5-xNdxCo0.5Al0.5Fe11.5O19 (x = 0.0, 0.01, 0.03, 0.05) were synthesized by applying the Sol–gel scheme. The samples were characterized via X-ray diffraction, vibrating sample magnetometer and scanning electron microscopy. The XRD results exposed that the structure was a hexagonal type with some extra peaks and c/a ratio was less than 3.98 which confirmed the M-type hexagonal structure. From VSM results, it was perceived that saturation magnetization enlarged up to 0.01 then dropped with Nd concentration while the coercivity decreased up to 0.01 and then high by the substitution of Nd. SEM showed that grains were platelet-like and grain growth decreased with Nd concentration. Electrical properties were measured and it was observed that AC resistivity dwindled with rising temperature which showed that the material was like a semiconductor. These ferrites may be suitable for perpendicular recording media.

Structural and Magnetic Properties of Rare Earth Doped Multilayer Nanocable Arrays.

The structure and anisotropic magnetization of One-dimensional (1D) Nd/Co/PA66 coaxial nanocables prepared by a low cost physical infiltration and electrodeposition methods are investigated. The preparation of Co nanotubes, Co/PA66 two-layer nanotubes and Nd/Co/PA66 three-layer nanocales is described, respectively. The structure, chemical composition and magnetic properties of various nanomaterials were investigated. The results show that the magnetic properties were affected by the rare earth metal Nd and the structural properties. The residual magnetization ratio of Nd/Co/PA66 nanocables is the biggest due to the synergistic effect of Nd and Co. In addition, the magnetization processes of the nanostructure were discussed in detail. We believe that these methods may provide an idea for ferromagnetic alloys and permanent magnet material and suitable for future applications in perpendicular recording media.

Structural, magnetic and Mössbauer analysis of lanthanum and nickel doped Co2Y-type hexaferrite nanomaterial matrix synthesized by sol-gel auto-combustion technique

Sol-gel auto-combustion technique was used to prepare the lanthanum (La3+) and nickel (Ni2+) doped Co2Y-type Sr2-yLayCo2NixFe12-xO22; x = 0.0, 0.1, 0.2, 0.3; y = 0.0, 0.01, 0.02, 0.03 nanohexaferrites materials. Synthesized nanohexaferrites were characterized by XRD, FTIR and EDS analysis. The collective XRD analysis reveals the single-phase patterns corresponding to various dopants concentration in the powder system matrix. The calculated structural - auxiliary parameters viz. Lattice constants (a and c), cell volume (Vcell), X-ray density (dx), bulk density (db) and porosity (P) have been found in range; a = 5.8798–5.8321 Å, c = 43.7316–44.7214 Å, Vcell = 1309.303–1317.304 Å3, dx = 5.014–4.987 gm/cm3, db = 3.774–3.128 gm/cm3 and P = 0.247–0.37. The XRD results were supported by FESEM and TEM images, which showed the plate-like shape of particles. Unlike irregular grains, regular platelet-like grains were composed of several crystallites with almost parallel c-axis and this is the most suitable shape for microwave absorption. Fourier-transform infrared spectroscopy (FTIR) showed the location of the ions including their respective bonds within the structure of the lattice matrix and variation of ion concentration was depicted by EDS analysis of the powder matrix. The investigation of magnetic properties was done by vibrating sample magnetometer (VSM). The saturation magnetization (Ms) and coercivity (Hc) were found to be in the range of 34.29–43.711 emu/g and 16.27–299.441 Oe, respectively. The improved values of Ms and Hc mean that these powders can be used as pre-eminent contestant materials for perpendicular recording media (PMR) applications. In addition, the synthesized Co2Y-type nanohexaferrites were characterized for the Mössbauer analysis at room temperature. The normal Zeeman (six-line patterns) splitting confirms the hexagonal phase of synthesized nanohexaferrites.

Structural, magnetic, and fluorescence properties of Nd/Ni/PA66 multilayer coaxial nanocables

Abstract One-dimensional (1D) Nd/Ni/PA66 multilayer nanocables were prepared in anodic aluminum oxide (AAO) template from outer layer to inner layer with physical wetting method and two-step electrochemical deposition method, respectively. The length of each layer is almost the same. SEM, TEM, XRD were employed to investigate the morphology and structure and chemical compositions. Magnetization measurements revealed that the Nd/Ni/PA66 nanocable arrays have greater coercivity and remanence ratio than the Ni and Ni/PA66 nanotubes and exhibited hard magnetism behavior. The easy axis was parallel to the long axis of nanocables. The interaction between each layer and the synergistic effect between iron and neodymium were explained in detail. In addition, the nanocables showed fluorescence properties due to the presence of Nd, and obvious emission peak at 401–472 nm was detected. We believe that these methods may provide an idea for ferromagnetic alloys and permanent magnet material and suitable for future applications in perpendicular recording media.

Abstract # 3216 High-fat diet induces memory impairments and hippocampal and hypothalamic astrogliosis

One-dimensional (1D) Nd/Ni/PA66 multilayer nanocables were prepared in anodic aluminum oxide (AAO) template from outer layer to inner layer with physical wetting method and two-step electrochemical deposition method, respectively. The length of each layer is almost the same. SEM, TEM, XRD were employed to investigate the morphology and structure and chemical compositions. Magnetization measurements revealed that the Nd/Ni/PA66 nanocable arrays have greater coercivity and remanence ratio than the Ni and Ni/PA66 nanotubes and exhibited hard magnetism behavior. The easy axis was parallel to the long axis of nanocables. The interaction between each layer and the synergistic effect between iron and neodymium were explained in detail. In addition, the nanocables showed fluorescence properties due to the presence of Nd, and obvious emission peak at 401–472 nm was detected. We believe that these methods may provide an idea for ferromagnetic alloys and permanent magnet material and suitable for future applications in perpendicular recording media.

Impact of Gd and Cu substitution on dielectric and magnetic properties of MnFeO3 multiferroic materials

Gadolinium (Gd) and copper (Cu) substituted MnFeO3 nanoparticles were synthesized via sol gel auto-combustion route. In imaginary electric modulus Debye peaks occurred which indicated the phenomenon of relaxation in the given frequency range. Cole-Cole plots were taken to investigate the contribution of grain and grain boundaries. The grain boundary resistance increased as compared to grain resistance with the incorporation of Gd and Cu. Magnetization and remanence were observed to decrease while coercivity (Hc) increased with Gd-Cu substitution. The phenomenon of super exchange interaction takes place between cations which reside on tetrahedral and octahedral sites. The magnetic ordering and spin canting were distorted with the substitution of Gd and Cu which leads to decrease in magnetic properties. The value of coercivity was raised upto 1992 Oe which proposed that synthesized multiferroics are useful in the fabrication of perpendicular recording media.

Alternating Magnetic Force Microscopy: Effect of Si doping on the temporal performance degradation of amorphous FeCoB magnetic tips

In order to increase the resolution of traditional MFM and extend its applications in the past, we created an Alternating Magnetic Force Microscopy (A-MFM) with a magnetic force modulation by applying an off-resonance AC magnetic field. A new magnetic tip has been developed for A-MFM in this work. Perpendicular magnetic recording medium with 500 kfci recording density is successfully imaged and analyzed by using the new tips coated by 6–15 nm amorphous FeCoSiB-based soft magnetic film. The effect of Si doping to the magnetic film on the A-MFM imaging was studied. It was found that Si additive had no effect on the imaging properties, such as signal-to-noise ratio and spatial resolution (kept at ∼5 nm level). But on other side, Si additive significantly degraded the chemical stability of FeCoSiB film due to oxidation in ambient atmosphere. Surface passivation by metal and boron oxides is considered to have a main effect on improvement of chemical stability of Si-free magnetic coating. The results have shown that Si-free FeCoB-based magnetic tips are appropriate candidates for A-MFM imaging in ambient conditions.

Microstructure and magnetic properties of FePt-(C,SiO2) granular films deposited on MgO, MgTiO, and MgTiON underlayers

We investigated the microstructure and magnetic properties of FePt-(C,SiO2) granular films deposited on MgO, MgTiO, and MgTiON underlayers. The coercivity and grain size of the FePt-(C,SiO2) film are substantially degraded when deposited on the MgTiO underlayer compared to those on the MgO underlayer, while they become comparable when deposited on the MgTiON underlayer. Atomic resolution STEM-EDS showed Ti in the MgTiO underlayer diffuses into FePt grains, while it is suppressed using the MgTiON underlayer. This suggests that MgTiON is a good choice for a conductive underlayer for growing L10-FePt perpendicular recording media for heat assisted magnetic recording.

Effect of heat-treatment on the magnetic and optical properties of Sr0.7Al0.3Fe11.4Mn0.6O19

Sr0.7Al0.3Fe11.4Mn0.6O19 was synthesized by sol-gel technique and sintered at varying temperatures 750 °C, 850 °C, 950 °C and 1050 °C for 5 h. We investigate the role of heat-treatment on the structural, magnetic and optical properties of Al–Mn doped strontium hexaferrite. XRD analysis indicates the formation of M-type hexaferrites with some traces of α-Fe2O3. The presence of two prominent peaks between 400 cm−1 and 600 cm−1 in the spectra of FTIR gives the possibility of the emergence of M-type hexagonal ferrites. FESEM micrograph shows that the grains of the prepared sample possess Plate-like hexagonal structure. EDX spectra confirmed the stoichiometry of the prepared sample. Recrystallization of the synthesized sample and formation temperature of 650 °C is observed in TGA analysis. Variation of the sintering temperature results in decrease of the band gap. Magnetic parameters were calculated from the M–H loop obtained from vibrating sample magnetometer (VSM). High value of coercivity (6750 Oe) is observed at 850 °C. Remanent and saturation magnetization decreases with increase heat-treatment temperature. The synthesized sample may be useful in perpendicular recording medium (PRM) and high frequency application.

Architecture for Hard Disk Drives

Magnetic data storage has made rapid progress in terms of areal density over the past few decades. Current products have areal density levels that exceed 1012 bits per square inch, about 1000 times greater than areal densities of the mid-1990s. Five component technologies have become hard-disk-drive industry standards over the past two decades: read heads based on giant magnetoresistance or tunneling magnetoresistance, perpendicular write heads, perpendicular recording media, heaters, and contact detection sensors. At the recording system level, shingled magnetic recording has been implemented by all disk-drive companies, but it has not become a new standard due to the additional penalty in access time (or latency). Here, interlaced magnetic recording and blocked magnetic recording are introduced and compared with conventional and shingled magnetic recording.

Quantification of intergranular exchange coupling in CoPtCr-based perpendicular recording media via ferromagnetic resonance measurements

Intergranular exchange fields in CoPtCr granular media materials were quantified through ferromagnetic resonance measurements in various magnetic states. The data indicate that the exchange field in CoPtCr granular films with no oxide segregant is comparable to the saturation magnetization of the films. With an introduction of a SiO2 segregant, however, the exchange field decreases. A 30% volume fraction of the segregant reduces the strength of the intergranular exchange coupling to zero.

1-6 二層垂直記録媒体のためのPRML方式の一検討

1-6 二層垂直記録媒体のためのPRML方式の一検討

Investigation of structural, dielectric and magnetic properties of Ho substituted nanostructured lithium ferrites synthesized via auto-citric combustion route

Abstract A comprehensive study on structural, spectral, magnetic and dielectric properties of holmium substituted (Ho3+) lithium ferrites; Li1.2Co0.4HoxFe2−xO4 (x = 0.00–0.15) synthesized via auto-citric combustion route has been carried out. The annealing temperature essential for complete decomposition of precipitates and spinel phase formation was found around 950 °C which was estimated from thermo-gravimetric analysis (TGA). The development of face centered cubic (FCC) spinel structure was confirmed from X-ray diffraction (XRD) analysis. However, the traces of an ortho phase (HoFeO3) were appeared for x ≥ 0.06 indicating the solubility limit of Ho3+ ions. The lattice constant ′a′ increased from 8.351 to 8.360 A upon Ho addition up to x = 0.06 and it decreased thereafter from 8.360 to 8.352 A. This decrease in lattice constant was attributed to the secondary phase formation revealing segregation of Ho3+ ions at grain boundaries. The porosity was found to decrease from 44 to 23% by the inclusion of Ho3+ ions. Fourier transform infrared spectra (FTIR) exhibited tetrahedral (v1) and octahedral (v2) intrinsic vibrational bands at 627 cm−1 and 479 cm−1 respectively and these bands revealed a shift with increasing Ho concentration. The variations in force constants (Ko and Kt) were calculated and discussed with the tetrahedral (rA) and octahedral (rB) bond length trends. The dielectric parameters have been investigated as a function of composition and frequency. The systematic addition of Ho gradually increased the ac conductivity from 8.97 × 103 to 5.56 × 104 (Ω-cm)−1 up to x = 0.12 and it subsequently decreased for x = 0.15. The complex impedance examination (Cole-Cole plots) confirmed a grain-interior phenomenon, effectively contributing to the dielectric properties. The coercivity was enhanced while the saturation magnetization (Ms) was lessened by the incorporation of Ho3+ ions. The maximum value of coercivity (706 Oe) was obtained for Li1.2Co0.4Ho0.12Fe1.88O4. The improved coercivity may suggest their utilization in perpendicular recording media applications.

Investigation of structural and magnetic properties of Zr-Co doped nickel ferrite nanomaterials

Nano-sized Zr-Co doped nickel ferrites with nominal composition, NiZrxCoxFe2-2xO4 (x=0.0, 0.2, 0.4, 0.6, 0.8) were synthesized using the micro-emulsion route. The structural elucidation of the synthesized materials was carried out by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The XRD analysis confirmed face centered cubic (FCC) structure of all compositions of NiZrxCoxFe2-2xO4 nanocrystallites. Crystallite size was calculated by Scherrer's formula found in the range 10–15nm. The variation in lattice parameter as determined by XRD data agreed with size variation of host (Fe3+) and guest (Zr4+ and Co2+) cations. FTIR spectra of doped NiFe2O4 exhibited the typical octahedral bands at 528.4cm−1 which is the characteristic feature of spinel structure of spinel ferrites. The characterized spinel NiZrxCoxFe2-2xO4 nano-ferrites were evaluated for their potential applications by magnetic hysteresis loops and dielectric measurements. The value of saturation magnetization (Ms) decreased from 47.9 to 13.09emu/g up to x=0.8 with ups and downs fluctuations in between x=0.0 to x=0.8. The high values of Ms of some compositions predicted the potential applications in high density perpendicular recording media and microwave devices. The frequency dependent behavior of permittivity (ε') is recorded and discussed with the help of hopping mechanism of both holes and electrons. The dielectric and magnetic data of NiZrxCoxFe2-2xO4 nano-ferrites suggested the potential applications of these ferrite nanoparticles in high frequency and magnetic data storage devices fabrication.

Self-assembled Co-BaZrO3 nanocomposite thin films with ultra-fine vertically aligned Co nanopillars.

A simple one-step pulsed laser deposition (PLD) method has been applied to grow self-assembled metal-oxide nanocomposite thin films. The as-deposited Co-BaZrO3 films show high epitaxial quality with ultra-fine vertically aligned Co nanopillars (diameter <5 nm) embedded in a BZO matrix. The diameter of the nanopillars can be further tuned by varying the deposition frequency. The metal and oxide phases grow separately without inter-diffusion or mixing. Taking advantage of this unique structure, a high saturation magnetization of ∼1375 emu cm-3 in the Co-BaZrO3 nanocomposites has been achieved and further confirmed by Lorentz microscopy imaging in TEM. Furthermore, the coercivity values of this nanocomposite thin films range from 600 Oe (20 Hz) to 1020 Oe (2 Hz), which makes the nanocomposite an ideal candidate for high-density perpendicular recording media.

Preparation and Characterization of Dedicated Servo Media

The dedicated servo media (DSM) is the conventional perpendicular magnetic recording (PMR) media with an inserted servo recording layer between the data recording layer and the soft underlayer. By using the conventional PMR media as the reference, the design consideration on the layer structure, the preparation, the magnetic properties, the microstructure, including the $c$ -axis orientation and the growth of the layers, the surface roughness, and the recording performance for the DSM are reported.