Measurement of the distribution of anisotropy constants in magnetic nanoparticles for hyperthermia applications

TY - JOUR

T1 - Measurement of the distribution of anisotropy constants in magnetic nanoparticles for hyperthermia applications

AU - McGhie, A

AU - Marquina, C

AU - O'Grady, Kevin Dermot

AU - Vallejo Fernandez, Gonzalo

N1 - © 2017, IOP Publishing Ltd. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

PY - 2017/10/16

Y1 - 2017/10/16

N2 - In this work we have applied theoretical calculations to new experimental measurements of the effect of the anisotropy distribution in magnetite nanoparticles which in turn controls hysteresis heating for hyperthermia applications. Good agreement between theory and experiment is reported where the theoretical calculation is based upon the detailed measurement of the particle elongation generally observed in the nanoparticles. The elongation has been measured from studies via transmission electron microscopy (TEM). We find that particle elongation is responsible for the anisotropy dispersion which can be obtained by analysis and fitting to a measurement of the temperature decay of remanence. A median value of the anisotropy constant of 1.5x105erg/cc was obtained. A very wide distribution of anisotropy constants is present with a Gaussian standard deviation of 1.5x105erg/cc. From our measurements, deviations in the value of the saturation magnetisation from particle to particle are most likely the main factor giving rise to this large distribution with 33% arising from the error in the measured elongation. The lower limit to the anisotropy constant of the nanoparticles is determined by the magnetocrystalline anisotropy of the material, 1.1x105erg/cc for magnetite which was studied in this work.

AB - In this work we have applied theoretical calculations to new experimental measurements of the effect of the anisotropy distribution in magnetite nanoparticles which in turn controls hysteresis heating for hyperthermia applications. Good agreement between theory and experiment is reported where the theoretical calculation is based upon the detailed measurement of the particle elongation generally observed in the nanoparticles. The elongation has been measured from studies via transmission electron microscopy (TEM). We find that particle elongation is responsible for the anisotropy dispersion which can be obtained by analysis and fitting to a measurement of the temperature decay of remanence. A median value of the anisotropy constant of 1.5x105erg/cc was obtained. A very wide distribution of anisotropy constants is present with a Gaussian standard deviation of 1.5x105erg/cc. From our measurements, deviations in the value of the saturation magnetisation from particle to particle are most likely the main factor giving rise to this large distribution with 33% arising from the error in the measured elongation. The lower limit to the anisotropy constant of the nanoparticles is determined by the magnetocrystalline anisotropy of the material, 1.1x105erg/cc for magnetite which was studied in this work.

M3 - Article

VL - 50

JO - Journal of Physics D: Applied Physics

JF - Journal of Physics D: Applied Physics

SN - 1361-6463

M1 - 455003

ER -