Charged magnetic domain walls as observed in nanostructured thin films: dependence on both film thickness and anisotropy

Abstract

The magnetic domain configurations of soft magnetic, nanostructured, pulsed laser-deposited Co films were investigated. Their dependence on both the thickness t (20 nm ≤ t ≤ 200 nm) and the anisotropy was studied. Charged zigzag walls, with a characteristic saw-tooth vertex angle θ, were observed. θ changed with t from θ ≈ 17° to ≈25°, presenting an intermediate sharp maximum that has not been described before. The reduced length of the zigzag walls also exhibited a peak at t ≈ 70 nm. The relationship between the total reduced length and the density energy of the magnetic wall allowed us to establish a change from a Néel-type to a Bloch-type core of the zigzag walls at this thickness, t ≈ 70 nm. We also accounted for the magnetic energy arising from the surface roughness of the thinner films after imaging the film surface morphologies. Moreover, this distinctive behaviour of the zigzag walls of these low-anisotropy films was compared to that of high-anisotropy films.

Surface Roughness Influence on Néel-, Crosstie, and Bloch-Type Charged Zigzag Magnetic Domain Walls in Nanostructured Fe Films

“…Fe films were prepared by pulsed laser deposition (PLD). This technique is a suitable and versatile method of preparing an extensive range of thin films, including magnetic films [ 13 , 14 , 15 , 34 , 35 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 ]. We used a chamber (Neocera, Beltsville, MD, USA) at a base vacuum pressure of 10 –6 mbar.…”

“…A custom-made substrate holder allowed the substrates to rotate at 120 rpm around an axis perpendicular to the substrate’s plane to minimize possible anisotropy caused by the non-uniform distribution of the laser beam’s energy. We used the following deposition parameters and conditions: Nd:YAG laser with its fundamental wavelength, particular fluence, glass and Si substrates, target-to substrate distance, normal incidence, and deposition time; from our previous works and from other studies [ 34 , 35 , 44 , 45 , 50 , 51 , 52 ], because we knew that they allow the controlled growth of nanostructured (grain size around 1–2 nm) soft magnetic films.…”

“…Several models have dealt with micromagnetic calculations of the magnetization distribution within zigzag walls, and some models have also included the dynamic hysteresis from such walls [ 30 , 31 , 32 ]. Charged zigzag domain walls have been observed in different systems, such as CoGd and CoGdNi [ 33 ], including, more recently, pulsed laser-deposited Co thin films [ 34 , 35 ] (and references therein), epitaxial Fe films grown on GaAs [ 36 ], permalloy/niobium bilayers [ 37 ], SmCo amorphous films [ 38 ], FePt thin films [ 39 ], CoFeB antiferromagnetically coupled layers [ 40 ], ultrathin yttrium iron garnet/Pt bilayers [ 41 ], single crystals of ferromagnetic shape memory Co 50 Ni 20 FeGa 29 alloy [ 42 ], and highly anisotropic CoFeB thin films [ 43 ]. However, to date, no experimental research has shown the transition from Néel- to Bloch-type cores with the formation of crosstie cores in Fe-charged domain walls.…”

Combined effects of vertical and lateral confinement on the magnetic properties of MnAs micro and nano-ribbons

“…As their thickness decreases, they exhibit a larger split of domains whose average size decreases. 24,25 These results are understood by noting that in these ribbons, the domain size is smaller than the ribbons width but larger than their thickness.…”

Imprinted Magnetic Anisotropy and Zigzag Domain Structure of Amorphous TbCo Films

“…Despite the interest to RE-TM systems both from the fundamental point of view and applications, their domain structure remains not well understood. For TM and RE-TM films with in-plane uniaxial anisotropy zigzag domains have been often observed [23][24][25][26] as a consequence of the equilibrium state between magnetostatic, exchange, and anisotropy energies. The surface energy of the zigzag wall consists of four terms: (1) The surface energy in the domain wall spine proper, which is either Bloch, Néel, or cross-tie types.…”