Photon Factory Activity Report 2022 #40 (2023)
BL-16A/2021G501

Probing Electronic and Magnetic Properties of Co1.5Fe1.5O4 Nanoparticles using X-ray
Magnetic Circular Dichroism
A. KUMARI1, S. JENA1, R. PAL2, V K. VERMA3, K. AMEMIYA4 andV. R. SINGH1*
1

Department of Physics, Central University of South Bihar, Gaya 824236

2

Department of Chemistry, Madanapalle Institute of Technology & Science, Angallu,
Madanapalle 517325, India
3

Department of Physics, VIT-AP University, Amaravati 522237 A.P. India

4

Photon Factory, IMSS, High Energy Accelerator Research Organization, Tsukuba,
Ibaraki 305-0801, Japan

Introduction:The
multifunctional
behaviour of spinel-structured magneticoxides, with the formula unit AB2O4, has
attracted a lot of interest in recent years. It
has broad applications in the fields ofmagnetically driven sensors, switches,
microelectronic devices, etc. The wellknown member of ferromagnetic ferrites i.e.,
CoxFe3-xO4 is a very promising material forthe designing of peculiar behaviour byaltering the preparation method, Co
concentration, and grain size-dependent
magnetic parameters such as magnetization,
coercivity, blocking of ferromagnetic
domains [1]. At one end of the CoxFe3-xO4series, the ferrimagnet magnetite isdistributed with a magnetic moment of 4μB/f.u. and a Curie temperature (TC) ⁓850 K.
On the other hand, an antiferromagnetic
Co3O4 is distributed at another end which has
a Neel temperature ⁓30 K. Henceforth, theCoxFe3-xO4 series with cation distribution(Co2+1- xFe3+x) [Co2+xFe3+2-x] O4 is regarded
the best candidate for changing themechanism of cation site exchange, a broad
range of magnetic moment and TC [2-4].
Magneto-crystalline anisotropy is a key
factor in influencing the TC, Hc, andspontaneous magnetization of Co ferrites i.e.,
CoFe2O4 as well as the blocking behaviour offerromagnetic domains. Although it ispossible to obtain a variety of magnetic
properties appropriate for room temperature
uses, the magnetic properties in the Co-richside of the CoxFe3-xO4 series have received

less attention. Therefore, more research on
the Co-rich side of ferrites is required forboth fundamental understanding and thedevelopment of ferrites for technologicaluses [1].
For this work, we have selected atypical chemical route synthesized ferrite
Co1.5Fe1.5O4 (CFO) nanoparticles with Coand Fe in the ratio of 50:50, for analyzing its
magnetization behaviour. The advanced
synchrotron-based
X-ray
Absorption
Spectroscopy (XAS) and X-ray Magnetic
Circular Dichroism (XMCD) measurements
for the CFO samples were carried out tounveil the magnetization behaviour of thematerial.
Experiment: The polycrystalline CFO
nanopowder was synthesized via a chemicalroute. The precursor solution was preparedby dissolving stoichiometric amounts of Co(NO3)2. 6H2O and Fe (NO3)3. 9H2O salts into
DI H2O, which was stirred for 10 min until atransparent aqueous solution get formed. TheNaOH solution was then added drop-wise instirring condition of the resultant solution
until a pH ⁓12 is reached. The solution washeated at 100–110º C with magnetic stirringfor 2 h, followed by heating at 140–150º C
for 1 h. The black-coloured gel formed waswashed several times with DI water and wasdried at 110º C. The fluffy black ash wasground to get fine powder of CFO, which wasmade into pellets. The CFO pellet sample

Photon Factory Activity Report 2022 #40 (2023)

was annealed at 200º C for 2 h. The sample's
purity was validated by the X-ray powder
Diffraction results, which showed no sign ofcontamination.
X-ray
spectroscopy,scattering, and imaging studies wereconducted at the Photon Factory's variable
polarisation soft x-ray beam-line BL-16A(KEK, Japan). Figure. 1 and 2 shows theexperimental geometry for the soft x-ray
absorption (XAS) and x-ray magnetic
circular dichroism (XMCD) studies. Thesample was positioned in the 10-9 Torr
vacuum room with a 5 T superconducting
magnet. XAS and XMCD signals weremeasured using the surface-sensitive total
electron yield (TEY) mode near Co L2,3 andFe L2,3 absorption edges with right and left
circularly polarised (RCP and LCP) x-rays,
with an energy resolution of ~ 0.1 eV, at 0T,
1T, and 2T varying magnetic fields (only thedata of 1T has been produced here).

Figure 1(a) Normalised XAS spectra, 1(b) Normalised XMCD spectra of Fe L-edge at appliedfield of 1T. 1(c)XMCD intensity ratio for Fe L-edge w.r.t applied field of 0T, 1T and 2T.

Figure 2(a) Normalised XAS spectra, 2(b) Normalised XMCD spectra of Co L-edge at appliedfield of 1T and 2(c) XMCD intensity ratio for Co L-edge w.r.t applied field of 0T, 1T and 2T
respectively.
Results and Discussions: The XAS spectra
obtained with applied magnetic fields of +1.0
and -1.0T are represented by μ+ and μ-. The
symbol μ+ and μ- represents left and rightcircularly polarized light as depicted inFigure 1(a) and 2(a). The XMCD spectrum
was collected by taking a difference of two
XAS spectra with negative and positive
helicity of the circularly polarized light. It is
known from the literature that; CFO acts as
soft-ferromagnetic at room temperatures. Inthe CFO, the Fe and Co absorption spectra
both shows a multiplet structure at the L3edges. From XAS spectra Co L edge, it isclear that Co shows multiple absorption peakat L3 edge along with a satellite peak
positioned at E= 779.07 eV; here the L2 peakshows singlet feature at 795.12 eV. Wellresolved peaks at the absorption maxima ofFe L3-edge at E = 710.13 eV and 708.75 eVexhibits a doublet structure at the L3 edge,
whereas, maxima at E = 721.9 eV at L2 edge

Photon Factory Activity Report 2022 #40 (2023)

is clearly observable. This verifies that thefine structures of the Fe 2p → 3d transition
should result from the localization of Fe 3delectrons rather than the oxidation of thesurface. Henceforth, based on obtained result
it can be concluded that unlike Fe, Co 2p toCo 3d transition is not-localized and infuses
more oxidation of the material. XMCD
signal collected for Co L2,3 and Fe L2,3 edges
at the H=1T, are depicted in Figure 1(b) and2(b). The XMCD signal at the Fe L2 edge andCo L2 edge is notably suppressed, indicating
magnetic ordering due to fully occupied t2g
level. The XMCD intensity w.r.t. the variablemagnetic field with 0T, 1T and 2T are shownin Figure 1(c) for Co and Fe-edges. This
result is quite relatable with the XMCD
graphs. Figure 1(c) and 2(c) exhibits that theintensity ratio of XMCD is increasing withincreasing magnetic-field.
Acknowledgements: The experiments at thePhoton Factory was approved by theProgram Advisory Committee (Proposal
Nos. 2021G501). Authors acknowledges
support from UGC-BSR Start-up Research
Grant F. 30-395/2017(BSR).
References:
1. R.N. Bhowmik, A.T. Satya, A. Bharathi, J.
Alloys Compd 559, 134–141 (2013).
2. G.H. Jonker, J. Phys. Chem. Solids 9, 165(1959).
3. A.V. Ramos, J.-B. Moussy, M.-J. Guittet,
M.G. Soyer, C. Gatel, P.B. Guillemaud,
B.W. Fonrose, E. Snoeck, Phys. Rev. B 75,224421 (2007).
4. V.G. Harris, A. Geiler, Y. Chen, S.D.
Yoon, M. Wu, A. Yang, Z. Chen, P. He, P.V.
Parimi, X. Zuo, C.E. Patton, M. Abe, O.
Acher, C. Vittoria, J. Magn. Magn. Mater.
321, 2035 (2009).
*Corresponding Email: vijayraj@cusb.ac.in