Nanoscale physics 

The effect of the domain wall on the magnetocaloric effect 
in cylindrical ferromagnetic nanowires 
Shevchenko A.B.1, Barabash M.Yu.2
1G.V. Kurdymov Institute of Metal Physics of the NAS of Ukraine, 36 Vernadskogo pr., 03680, Kyiv-142, Ukraine 
2Technical Centre of the NAS of Ukraine, 13 Pokrovskya str., 04070, Kyiv, Ukraine 
E-mail: bashik_77@ukr.net 

The magnetocaloric effect (MCE) in cylindrical ferrite-garnet, nickel and iron nanowires containing a domain wall (DW) was investigated [1-3]. A negative MCE was found out in these systems in a weak magnetic field, caused by thermal motion of the DW. The conditions for this phenomenon are determined. It is shown that a reduction in the magnetization of nanowires causes an increase of their critical diameters at which negative MCE occurs. 
It was established that by means of negative MCE it is possible to increase (or to decrease with the opposite change of magnetic field) the temperature of a compact comprised of 103-104 cylindrical ferromagnetic nanowires by ~ 1K. It is clear that, using a series of similar compact sets of nanowires, one can obtain (after thermodynamic equilibrium is reached) a noticeable increase (or decrease) in the initial temperature of the environment. This result is of practical interest for the development of new technologies based on the thermomagnetic properties of nanowires: e.g., for the elimination of cancer cells in oncology. 
In the turn, in the absence of DW in ferromagnetic nanowires a weaker positive MCE occurs in a weak magnetic field. 

1.	Shevchenko A. B., Barabash M. Yu. Heat capacity of ferrite – garnet nanowire with domain wall // Phys. B: Cond. Matters.-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). 
3.	Shevchenko A. B., Barabash M. Yu. Magnetocaloric effect in nickel and iron nanowires with a domain wall // Appl. Nanoscience.-2021.- 
https://doi.org/10.1007/s13204-020-01649-8