arXiv subjects

I. Suzuki

Publications and source records attributed to I. Suzuki.

4 recordsLinked to original sources

arXiv2026

Phase-Transition Induced Magnetic Domain Evolution and Magnetization Dynamics in FePt/FeRh Bilayers for Advanced Heat-Assisted Magnetic Recording

Achieving ultrahigh recording densities with low power consumption is a central challenge for next generation heat assisted magnetic recording (HAMR), as conventional L10 FePt media require intense laser heating due to their high coercivity (Hc) and high Curie temperature (700 K). Here, we address this issue using FePt/FeRh bilayers, where the antiferromagnetic to ferromagnetic transition of FeRh near 350 K generates strong interfacial exchange coupling that assists magnetization switching in the FePt layer. Magnetometry measurements reveal a 40% reduction in Hc from 300 K to 400 K in the bilayer, compared to only 8% in single layer FePt. Temperature dependent MFM directly captures phase transition induced domain evolution, showing a 30% reduction in domain size and enhanced phase contrast. TR-MOKE measurements reveal only a minor (0.4 T) modification of the effective anisotropy field during phase transition, confirming that the intrinsic anisotropy of FePt remains largely preserved. These results demonstrate that the reduction in Hc in FePt/FeRh bilayers is primarily governed by phase transition induced domain wall mobility coupled with interfacial magnetic interactions, rather than by intrinsic anisotropy softening. This mechanism provides a pathway toward efficient magnetization switching under reduced thermal load, making FePt/FeRh heterostructures promising candidates for advanced HAMR media.

cond-mat.mtrl-sci↗

arXiv2023

Multi-level recording in dual-layer FePt-C granular film for heat-assisted magnetic recording

Multi-level magnetic recording is a new concept for increasing the data storage capacity of hard disk drives. However, its implementation has been limited by a lack of suitable media capable of storing information at multiple levels. Herein, we overcome this problem by developing dual FePt-C nanogranular films separated by a Ru-C breaking layer with a cubic crystal structure. The FePt grains in the bottom and top layers of the developed media exhibited different effective magnetocrystalline anisotropies and Curie temperatures. The former is realized by different degrees of ordering in the L10-FePt grains, whereas the latter was attributed to the diffusion of Ru, thereby enabling separate magnetic recordings at each layer under different magnetic fields and temperatures. Furthermore, the magnetic measurements and heat-assisted magnetic recording simulations showed that these media enabled 3-level recording and could potentially be extended to 4-level recording, as the up-down and down-up states exhibited non-zero magnetization.

cond-mat.mtrl-sci↗

arXiv2003

The CMS Event Builder

The data acquisition system of the CMS experiment at the Large Hadron Collider will employ an event builder which will combine data from about 500 data sources into full events at an aggregate throughput of 100 GByte/s. Several architectures and switch technologies have been evaluated for the DAQ Technical Design Report by measurements with test benches and by simulation. This paper describes studies of an EVB test-bench based on 64 PCs acting as data sources and data consumers and employing both Gigabit Ethernet and Myrinet technologies as the interconnect. In the case of Ethernet, protocols based on Layer-2 frames and on TCP/IP are evaluated. Results from ongoing studies, including measurements on throughput and scaling are presented. The architecture of the baseline CMS event builder will be outlined. The event builder is organised into two stages with intelligent buffers in between. The first stage contains 64 switches performing a first level of data concentration by building super-fragments from fragments of 8 data sources. The second stage combines the 64 super-fragments into full events. This architecture allows installation of the second stage of the event builder in steps, with the overall throughput scaling linearly with the number of switches in the second stage. Possible implementations of the components of the event builder are discussed and the expected performance of the full event builder is outlined.

physics.ins-det↗

arXiv2003

Using XDAQ in Application Scenarios of the CMS Experiment

XDAQ is a generic data acquisition software environment that emerged from a rich set of of use-cases encountered in the CMS experiment. They cover not the deployment for multiple sub-detectors and the operation of different processing and networking equipment as well as a distributed collaboration of users with different needs. The use of the software in various application scenarios demonstrated the viability of the approach. We discuss two applications, the tracker local DAQ system for front-end commissioning and the muon chamber validation system. The description is completed by a brief overview of XDAQ.

hep-ex↗