Correlated spin canting in ordered core-shellFe3O4/MnxFe3−xO4

Abstract

Polarization-analyzed small-angle neutron scattering methods are used to determine the spin arrangements and experimental length scales of magnetic correlations in ordered three-dimensional assemblies of ∼ 7.4 nm diameter core-shell Fe 3 O 4 /Mn x Fe 3−x O 4 nanoparticles. In moderate to high magnetic fields, the assemblies display a canted magnetic structure where the canting direction is coherent from nanoparticle to nanoparticle, in contrast to the less extended, more single particle-like behavior for similar ferrite assemblies. The observed magnetic scattering is modeled by assuming that the interparticle dipolar coupling combined with Zeeman effects in a field leads to nanoparticle domains with preferred net spin alignments relative to packing symmetry axes. Over a range of fields and temperatures, the model qualitatively explains the observed scattering anomalies in terms of clusters that vary in area and thickness, highlighting the complex structures adopted in real, dense nanoparticle systems. The clusters often have a strong two-dimensional magnetic character which is attributed to structural stacking faults and the resulting influence of interparticle dipolar interactions for these magnetically soft nanoparticles.

Spin Canting in Exchange Coupled Bi-Magnetic Nanoparticles: Interfacial Effects and Hard / Soft Layer Ordering

“…The presence of parallel and perpendicular magnetic Bragg peaks in Fig. 6 for both NP systems is indicative of a coherent spin structure that persists across NPs instead of an isolated particle magnetic structure [16,17,50]. Referring to Fig.…”

Hybrid magnetic nanoparticles as efficient nanoheaters in biomedical applications

“…The magnetization of small MNPs is usually lower than bulk counterparts due to the canting of spins at the surface; 168,172,173 however, core/shell exchange coupled HNPs revealed interfacemediated spin congurations different than their single-phase counterparts. 131, [174][175][176] When the shell layer is ultrathin, i.e. a few atomic layers-thick, novel and oen unexplained properties have been reported, comprising unexpectedly large anisotropies or coercivity gradients, probably associated to complex spin arrangements at the atomic level.…”

Anisometric mesoscale nuclear and magnetic texture in sintered Nd-Fe-B magnets

“…The SANS technique (see [11] for a recent review) provides statistically averaged bulk information about both the structural and magnetic correlations on a length scale between a few and a few hundred nanometers. This method has previously been applied to study the structures of magnetic nanoparticles [12][13][14][15][16][17][18][19][20], soft magnetic nanocomposites [21,22], proton domains [23][24][25], magnetic steels [26][27][28][29][30], or Heuslertype alloys [31][32][33][34][35]. Regarding Nd-Fe-B, SANS investigations [8,36] have reported a peculiar cross-shaped angular anisotropy in the scattering cross section of the polycrystalline textured material.…”