NMR-spin-echo study of pinning of domain walls in cobalt micropowders, nanopowders and nanowires

Tsisana Gavasheli; Grigor Mamniashvili; Giorgi Ghvedashvili; Tatiana Gegechkori

doi:10.3103/S0735272723080058

Authors

Tsisana Gavasheli Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia https://orcid.org/0000-0002-8915-0982
Grigor Mamniashvili Ivane Javakhishvili Tbilisi State University Andronikashvili Institute of Physics, Tbilisi, Georgia https://orcid.org/0000-0001-8344-0885
Giorgi Ghvedashvili Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia https://orcid.org/0000-0002-8989-0593
Tatiana Gegechkori Ivane Javakhishvili Tbilisi State University Andronikashvili Institute of Physics, Tbilisi, Georgia

DOI:

https://doi.org/10.3103/S0735272723080058

Keywords:

nuclear spin echo, magnetic video pulse, single-pulse echo, double-pulse echo, cobalt, pinning

Abstract

The pinning of domain walls in cobalt micropowders, nanopowders, and nanowires is studied by the double-pulse spin-echo NMR method under an additional magnetic video pulse. Cobalt micropowders are obtained by melting in an induction furnace. Nanopowders are produced using electron beam technology and chemical deposition. This chemical deposition reaction is carried out in an external magnetic field to obtain nanowires.

The pinning in these systems is measured as a function of the long-term magnetic video pulse and its amplitude. It is established that the magnetic video pulse area is constant for all its threshold values corresponding to the beginning of the double-pulse echo signal suppression. The linear nature of the pinning dependence on the external magnetic field magnitude in cobalt micropowders in a wider range of the external magnetic field change compared to lithium ferrite is presented. Alternative information about the pinning strength of domain walls in magnets can also be obtained by studying the magnetic video pulse influence on the magnetic echo signal formed by the joint action of radio frequency and magnetic pulses. These NMR methods can be used for microscopic control of the domain wall properties in the studied magnets with the aim of their potential use in functional materials, memory devices, and sensors.

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