3 Spin-Polarized Plasmonics: Fresh View …
65
Fig. 3.11 a The field dependence of magnetic moment of Co nanoparticles (0.69 mg) dispersed
in 10.31 g PMMA matrix taken at 5 K (blue line), 100 K (green line) and 298 K (red line).
b The field dependence of magnetization for 5 K and 298 K. Main panel shows magnetization
of Co-nanoparticles with subtracted diamagnetic contribution of PMMA host material. Top-left
inset shows as-measured magnetization at 5 and 298 K. Green dashed line shows the reference
line for diamagnetic contribution of host material. Bottom-right inset shows expanded view of
magnetization at low fields. From [2] with permission licensed under CC BY 4.0 https://creativec
ommons.org
magnetic dipoles. On the other hand, the coercive field at T = 5 K, H c = 0.145 T, is
comparable to reported fcc CoNP [60].
The magnetic moment per particle was calculated for 8.8 nm Co-NP (#25) from
the susceptibility χ above the blocking temperature at low field using following
equation [58]
χ =
M s μ
3k b T
,
(3.8)
where μ is the magnetic moment per particle, M s is the saturation magnetization, and
k b is Boltzmann’s constant. The diamagnetic susceptibility of the PMMA matrix was
measured and subtracted to obtain these results: At 214 K contribution of diamagnetic part (PMMA) for sample #25 is 0.45 × 10
−6 emu; Magnetic moment, m =
(18.8−0.45) × 10
−6 emu = 18.35 × 10
−6 emu; Saturation magnetization M s at T =
298 K (the same at 214 K): M s = 0.57 emu/g. Susceptibility χ measured for applied
field H = 20 Oe at 214 K: χ = m/(m ρ · H) = 18.35 × 10
−6 /(0.69 × 10
−3
× 20 Oe)
= 1.33 × 10
−3 emu/g Oe. Here m ρ = 0.69 mg is the mass of Co nanoparticles in
PMMA host material (10.31 mg). Thus, the magnetic moment per particle above T
= 214 K:
μ =
3k B T χ
M s
=
3 · 1.38 · 10
−16
· 214 · 1.33 · 10
−3
0.57
∼ = 2.07 · 10
−16 Erg/G (3.9)
65
Fig. 3.11 a The field dependence of magnetic moment of Co nanoparticles (0.69 mg) dispersed
in 10.31 g PMMA matrix taken at 5 K (blue line), 100 K (green line) and 298 K (red line).
b The field dependence of magnetization for 5 K and 298 K. Main panel shows magnetization
of Co-nanoparticles with subtracted diamagnetic contribution of PMMA host material. Top-left
inset shows as-measured magnetization at 5 and 298 K. Green dashed line shows the reference
line for diamagnetic contribution of host material. Bottom-right inset shows expanded view of
magnetization at low fields. From [2] with permission licensed under CC BY 4.0 https://creativec
ommons.org
magnetic dipoles. On the other hand, the coercive field at T = 5 K, H c = 0.145 T, is
comparable to reported fcc CoNP [60].
The magnetic moment per particle was calculated for 8.8 nm Co-NP (#25) from
the susceptibility χ above the blocking temperature at low field using following
equation [58]
χ =
M s μ
3k b T
,
(3.8)
where μ is the magnetic moment per particle, M s is the saturation magnetization, and
k b is Boltzmann’s constant. The diamagnetic susceptibility of the PMMA matrix was
measured and subtracted to obtain these results: At 214 K contribution of diamagnetic part (PMMA) for sample #25 is 0.45 × 10
−6 emu; Magnetic moment, m =
(18.8−0.45) × 10
−6 emu = 18.35 × 10
−6 emu; Saturation magnetization M s at T =
298 K (the same at 214 K): M s = 0.57 emu/g. Susceptibility χ measured for applied
field H = 20 Oe at 214 K: χ = m/(m ρ · H) = 18.35 × 10
−6 /(0.69 × 10
−3
× 20 Oe)
= 1.33 × 10
−3 emu/g Oe. Here m ρ = 0.69 mg is the mass of Co nanoparticles in
PMMA host material (10.31 mg). Thus, the magnetic moment per particle above T
= 214 K:
μ =
3k B T χ
M s
=
3 · 1.38 · 10
−16
· 214 · 1.33 · 10
−3
0.57
∼ = 2.07 · 10
−16 Erg/G (3.9)