Nanoscale physics 
The effect of the domain wall on the thermodynamic properties of cylindrical nickel nanowire 
A.B. Shevchenko1, M.Yu. Barabash2, G.G.Vlaykov2

1 G.V. Kurdymov Institute of Metal Physics, Natl. Acad. of Sci. of Ukraine. Prospect Vernadskogo, 36, Kiev-03142, Ukraine. 

2 Technical Centre of Natl. Acad. of Sci. of Ukraine. 
Str. Pokrovskya, 13, Kiev-04070, Ukraine. 
E-mail: mbararbash@nasu.kiev.ua 

The actual task of the physics of nanoscale systems is the study of ferromagnetic nanowires (FN). Due to their unique magnetic, thermodynamic and magnetocaloric properties, these objects are already widely used (or are promising materials) in various fields of modern technology and biomedicine It is obvious that, along with obtaining FNs, an important problem is the control of their physical properties. One of the directions in solving of this problem is the controlled dynamics of domain walls (DWs) which can be considered as nanoscale magnetic “impurities” in the FNs. Since there are practically no defects in a nanowire, the model of a domain wall moving with average velocity determined by the temperature of the system seems rather adequate [1]. In addition we will consider perfect FN without random fluctuations of the local crystallographic anisotropy and heterogeneities on the surface. Based on this approach, it was shown for a cylindrical nickel nanowire, that the entropy and heat capacity of the DW can be higher than or on the order of the analogous characteristics of the electron, magnon, and phonon (Debye) subsystems of FN. The conditions at which this effect takes place are determined. The methods of its strengthening are considered [2]. So, an increase in the length of nanowire and the number of DWs by a factor 10 increases its diameter at which the heat capacity of DW has the same order as the phonon subsystem by 33.5%. 

1.	Shevchenko A.B., Barabash M.Yu. Heat capacity of ferrite –garnet nanowire with domain wall. // Phys. B: Conden. Matt.-2019.-556, 
- P. 114-117. 
2.	Shevchenko A.B., Barabash M.Yu. The effect of the domain wall on the entropy and the heat capacity of nickel nanowire // Res. in Phys.-2020.-16, 
– P. 102988(5).