Magnetic interactions in the single layer copper and nickel hydroxides synthetized in the confined space of layered silicate*

Layered hydroxides, such as the copper hydroxide are quasi two dimensional magnetic materials whose structures consist of alternating stacking of the magnetic copper hydroxides and the carboxylate layers [1,2]. Its magnetic properties are fascinating, and it is the example of 2D Heisenberg spin ladder.

In our work, we prepared for the first time single-layer Cu(OH)₂ [3] and Ni(OH)₂, by synthesis inside the layered phyllosilicate sodium fluorohectorite clay (Fht) [4]. Fht is a structure composed of 1 nm thin sandwich of SiO₂ and metal oxides, and these sheets are negatively charged and kept together by interlayer cation.

We used several characterization techniques such as measurements of magnetic properties, X-ray diffraction and small angle neutron scattering. Instead of the single layer, hydroxide is in the form of app. 10 nm large 1 nm thin islands. For Cu(OH)₂, magnetic behaviour is very complex, exhibiting 3 types of magnetic interactions – in the Cu(OH)₂ itself, among the island inside the single interlayer and among islands across the Fht sheet.

So far, there is no method how to prepare single layers of Cu and Ni hydroxides, hence our method of synthesis in the confined space of layered silicate is very unique.

 

[1]. M. Suzuki, et al. Phys Rev B 64, 1–8 (2001) [2]. G. J. da Silva, et al. Phys Rev E 66, 1–8 (2002) [3] Wataru Fujita, et al. Appl Clay Sci 15, 281-303 (1999). [4]. H. Hemmen, et al. Langmuir 28,1678–1682 (2012)