Bi-component magnonic crystals have shown promising applications in magnonics and spintronics [1,2]. Arrays of two-dimensional exchange and magnetostatically coupled bi-component nanotriangles (BNTs) comprising of alternating permalloy (Py) and cobalt (Co) in hexagonal arrangement were fabricated by self-aligned stepwise nanosphere lithography [3]. The separation (S) between constituent NTs was varied to investigate the effects of exchange and magnetostatic interaction. Static magnetic properties of BNTs were investigated by OOMMF simulations and compared to homogeneous Py NTs [4]. Fig 1(a) shows simulated M-H loops for BNTs during hard axis magnetization with different S values. The loops exhibit distinct two-step switching corresponding to magnetization reversal of Py and Co NTs at different fields. Py NTs are observed to switch at a lower field shown in Fig 1(d) for S=0 nm. For homogeneous Py NTs in Fig 1(b), multiple kinks were also observed for S=0 & -60 nm (overlapping NTs) but these represent the domain changes in individual NTs. For S= -60nm, antiparallel alignment was displayed in each NT pair during reversal. For S=60nm, the NTs react independently due to the lack of strong exchange coupling. Hence switching is random and independent of location. For S=0, the NTs within the inner ring switched at a lower field, as shown in Fig 1(e). Fig 2 shows MFM images of BNTs with S=0 during hard axis field reversal. The magnetic domains of BNTs at remanence after saturation is in good agreement with simulation in Fig 1(c). In contrast to Fig 1(d), Co NTs were observed to reverse at a lower field. This is attributed to the smaller fabricated Co size compared to Py NTs. We will discuss the effect of material difference and separation between constituent NTs in detail via OOMMF simulation and field reversal study.

![](https://assets.underline.io/uploads/markdown_image/1/image/dae6f6f4d1da11df0bb2e846d9d8ecf2.jpg)

Fig. 1 Simulated M-H loops for S= -60, 0, +60 nm for (a) Co/Py NTs; (b) Py/Py NTs. Simulated spin states for (c-d) BNTs; (e) Py/Py NTs at different fields. Colored arrows indicate spin orientations.


![](https://assets.underline.io/uploads/markdown_image/1/image/8285bc51588ea41eb64cd46369774d8f.jpg)

Fig. 2 (a) AFM; (b-d) MFM of BNTs with S=0 nm at remanence after applying field of 3500, -400 and -600 Oe. White arrow indicates the applied field direction. Colored circles indicate a change in magnetic domain.

Static Magnetic Properties of Bi-component Nanotriangles in Hexagonal Arrangement Fabricated by Stepwise Nanosphere Lithography

**Session chairs:** Tom Thomson, University of Manchester and Hikaru Nomura, Yoshishige Suzuki Lab, Osaka University



EOF - Patterned Films

technical paper

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Haotian Su

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Static Magnetic Properties of Bi-component Nanotriangles in Hexagonal Arrangement Fabricated by Stepwise Nanosphere Lithography

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