Ferrimagnetic ${\mathrm{DyCo}}_{5}$ Nanostructures for Bits in Heat-Assisted Magnetic Recording

Ferrimagnetic ${DyCo}_{5}$ Nanostructures for Bits in Heat-Assisted Magnetic Recording

A. A. Ünal, S. Valencia, F. Radu, D. Marchenko, K. J. Merazzo, M. Vázquez, and J. Sánchez-Barriga

Phys. Rev. Applied 5, 064007 – Published 13 June 2016

Abstract

Increasing the magnetic data recording density requires reducing the size of the individual memory elements of a recording layer as well as employing magnetic materials with temperature-dependent functionalities. Therefore, we predict that the near future of magnetic data storage technology involves a combination of energy-assisted recording on nanometer-scale magnetic media. We present the potential of heat-assisted magnetic recording on a patterned sample; a ferrimagnetic alloy composed of a rare-earth and a transition metal ${DyCo}_{5}$ , which is grown on a hexagonal-ordered nanohole array membrane. The magnetization of the antidot array sample is out-of-plane oriented at room temperature and rotates towards in plane upon heating above its magnetic anisotropy reorientation temperature ( $T_{R}$ ) of 350 K, just above room temperature. Upon cooling back to room temperature (below $T_{R}$ ), we observe a well-defined and unexpected in-plane magnetic domain configuration modulating with 45 nm. We discuss the underlying mechanisms giving rise to this behavior by comparing the magnetic properties of the patterned sample with the ones of its extended thin-film counterpart. Our results pave the way for future applications of ferrimagnetic antidot arrays of superior functionality in magnetic nanodevices near room temperature.

Received 17 October 2015

DOI:https://doi.org/10.1103/PhysRevApplied.5.064007

Physics Subject Headings (PhySH)

Magnetic anisotropy Magnetization switching

Ferrimagnets Nanostructures Transition-metal rare-earth alloys

Scanning electron microscopy X-ray magnetic circular dichroism X-ray photoemission electron microscopy

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

A. A. Ünal¹, S. Valencia¹, F. Radu¹, D. Marchenko¹, K. J. Merazzo², M. Vázquez², and J. Sánchez-Barriga^1,*

¹Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Straße 15, 12489 Berlin, Germany
²Instituto de Ciencia de Materiales de Madrid, CSIC, 28049 Madrid, Spain

^*Corresponding author. jaime.sanchez-barriga@helmholtz-berlin.de.

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 5, Iss. 6 — June 2016

Subject Areas

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(a) SEM and (b) x-ray photoelectron emission microscopy (XPEEM) images of the hexagonal lattice antidot array of 68-nm pore size and 105-nm separation between pore centers. XAS spectra of (c) Co and (d) Dy elements at their $L_{2, 3}$ and $M_{4, 5}$ edges, as obtained from XPEEM energy scans extracted in the field of view seen in (b) using a x-ray beam of horizontal linear polarization.
Reuse & Permissions
Figure 2
XMCD-PEEM images measured at 385 K at the $Co − L_{3}$ and $Dy − M_{5}$ edges from the antidot array [(a),(b)] and the extended thin-film sample [(c),(d)] showing the ferrimagnetic ordering of the Co and Dy magnetic moments via the corresponding blue-red XMCD contrast in remanence. Antidots stabilize nanometer-sized domains separated from each other. The experimental geometry (bottom left) and top view of the incoming x-ray beam relative to the orientation of the XMCD-PEEM images (bottom right) are also shown.
Reuse & Permissions
Figure 3
XMCD-PEEM images measured at the Co- $L_{3}$ edge from the extended thin-film sample [(a)–(c)] and from the antidot array sample [(d)–(f)] in remanence at the labeled temperatures. On the right-hand side of the panels, a top view of the incoming x-ray beam is shown relative to the orientation of the XMCD-PEEM images. (g) Line profile along the structure of five neighboring antidots, XPEEM (black line) and SEM (dashed line). (h) Line profiles along XPEEM magnetic images for opposite magnetizations (blue and red lines) show magnetic information repeating every 45–50 nm (between the $M ↑$ and $M = 0$ states, and between the $M ↓$ and $M = 0$ states). We obtain this value by taking into account the full width at half maximum extracted from the line profiles across the magnetic domains.
Reuse & Permissions
Figure 4
(a) Schematic representation of the heat-assisted magnetic recording process and the magnetic anisotropy reorientation as observed by XPEEM. A selection of images at the $Co − L_{3}$ edge summarizes the experimental results. On the left, the room-temperature results correspond to different XMCD images of the antidot array. (b)–(d) Results of micromagnetic simulations. In (b), a SEM image from the antidot array superimposed with blue circles around the nanoholes is shown. The circles are used as a mask to construct the input for the calculations. The magnetic anisotropy is oriented along the $+ y$ direction, and the initial magnetization is out of plane. (c) Calculated multidomain configuration of the antidot array in the relaxed state. Small arrows depict the magnetization directions and blue and red colors the projection of the magnetization along the $y$ direction. (d) Same calculations as in (c) for the extended film revealing a single-domain configuration.
Reuse & Permissions
Figure 5
(a)–(c) XMCD-PEEM images obtained at the $Co − L_{3}$ edge upon heating the antidot sample once the in-plane magnetic domain configurations are reached at room temperature. Green and black dashed circles emphasize two distinct regions of the sample where the orientation of the in-plane magnetization remains unchanged or flips from red to blue contrast above $T_{R}$ , respectively. (d),(e) Similar images as in (a)–(c) obtained at a temperature of 470 K under an in-plane applied magnetic field of (d) 75 and (e) $- 150 Oe$ . (f) Corresponding hysteresis loop obtained from the region marked in (e) by a green dashed rectangle. The scale bars in (a) and (d) are the same as in (b),(c) and (d),(e), respectively. The experimental geometry (bottom left) and a top view of the incoming x-ray beam and applied magnetic field relative to the orientation of the XMCD-PEEM images (bottom right) are also indicated.
Reuse & Permissions

Physical Review Applied

Ferrimagnetic DyCo5 Nanostructures for Bits in Heat-Assisted Magnetic Recording

A. A. Ünal, S. Valencia, F. Radu, D. Marchenko, K. J. Merazzo, M. Vázquez, and J. Sánchez-Barriga

Phys. Rev. Applied 5, 064007 – Published 13 June 2016

Abstract

Physics Subject Headings (PhySH)

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Subject Areas

Access Options

Authorization Required

Other Options

Download & Share

Images

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Log In

Search

Article Lookup

Paste a citation or DOI

Enter a citation

Ferrimagnetic ${DyCo}_{5}$ Nanostructures for Bits in Heat-Assisted Magnetic Recording