Elucidating the origin of magnetic ordering in ferroelectric BaTiO<sub>3-</sub> <i>d</i> thin film via electronic structure modification

Majumder, Supriyo; Basera, Pooja; Tripathi, Malvika; Choudhary, R. J.; Bhattacharya, Saswata; Bapna, Komal; Phase, D. M.

doi:10.1088/1361-648x/ab06d5

Cited by 21 publications

(19 citation statements)

References 65 publications

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“…On the other hand, the possible presence O vacancy in lattice structure will modify the ligand field symmetry and electron hole ratio in transition metal d band. Consequently, the spectral shape and intensity of feature λ is a sensitive probe for the lattice oxygen content of the system [54,55]. We have observed that for different SNMO films with varying growth conditions, feature λ in O K XANES show similar spectral shape and weight (Inset of Fig.…”

Section: Resultsmentioning

confidence: 81%

Robust electronic and tunable magnetic states in Sm$ _{2} $NiMnO$ _{6} $ ferromagnetic insulator

Majumder,

Tripathi,

Píš

et al. 2022

Preprint

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Ferromagnetic insulators (FM-Is) are the materials of interest for new generation quantum electronic applications. Here, we have investigated the physical observables depicting FM-I ground states in epitaxial Sm 2 NiMnO 6 (SNMO) double perovskite thin films fabricated under different conditions to realize different level of Ni/Mn anti-site disorders (ASDs). The presence of ASDs immensely influence the characteristic magnetic and anisotropy behaviors in SNMO system by introducing short scale antiferromagnetic interactions in predominant long range FM ordered host matrix. Charge disproportion between cation sites in form of N i 2+ + M n 4+ −→ N i 3+ + M n 3+ , causes mixed valency in both Ni and Mn species, which is found insensitive to ASD concentrations. Temperature dependent photo emission, photo absorption measurements duly combined with cluster model configuration interaction simulations, suggest that the eigenstates of Ni and Mn cations can be satisfactorily described as a linear combination of the unscreened d n and screened d n+1 L (L: O 2p hole) states. The electronic structure across the Fermi level (E F ) exhibits closely spaced Ni 3d, Mn 3d and O 2p states. From occupied and unoccupied bands, estimated values of the Coulomb repulsion energy (U ) and ligand to metal charge transfer energy (∆), indicate charge transfer insulating nature, where remarkable modification in Ni/Mn 3d -O 2p hybridization takes place across the FM transition temperature. Existence of ASD broadens the Ni, Mn 3d spectral features, whereas spectral positions are found to be unaltered. Hereby, present work demonstrates SNMO thin film as a FM-I system, where FM state can be tuned by manipulating ASD in the crystal structure, while I state remains intact.

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Section: Resultsmentioning

confidence: 81%

Robust electronic and tunable magnetic states in Sm$ _{2} $NiMnO$ _{6} $ ferromagnetic insulator

Majumder,

Tripathi,

Píš

et al. 2022

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“…NPD refinement of Ni and Mn occupancies at 2c and 2d sites, reveals presence of ∼3.8(6)% and 11.8(8)% ASD in S O and S D samples, respectively. As the vacancy defects may influence the electronic and magnetic properties [36], it is also important to check the possible presence of cation or anion vacancy defects in SNMO system. The scattered X-ray intensity in PXRD measurements depend on electron density of the scattering atom, hence the contributions from heavy Z elements dominate over low Z elements and any attempt to determine atomic concentration of low Z element such as oxygen could be erroneous.…”

Section: Resultsmentioning

confidence: 99%

Microscopic insights of magnetism in Sm$ _{2} $NiMnO$ _{6} $ double perovskite

Majumder,

Tripathi,

Fischer

et al. 2022

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The functional characteristics of double perovskites with unique ferromagnetic-insulator ground state have been controversial due to the unavoidable presence of anti-site disorders (ASDs). Here, we aim to investigate the origin of magnetic ordering on local and global scales in Sm2NiMnO6 (SNMO) double perovskite system. Different calcination routes are exploited to generate different cation arrangements in SNMO and the corresponding magnetic configurations are examined using the high energy (E ∼0.3 eV) 'hot neutrons', which has helped to overcome Sm absorption as well as to record total (Bragg's+diffuse) scattering profiles with high momentum transfer (Qmax ∼24 Å−1 ). We have observed that the Ni-Mn sublattice adopts long range collinear ferromagnetic FxFz structure with commensurate k=(0, 0, 0) propagation vector, below ordering temperature T 160 K, irrespective of variable ASD concentrations. In addition, the signatures indicating the antiparallel polarization of Sm paramagnetic moments with respect to Ni-Mn network, are noticed in the vicinity of anomalous magnetic transitions at T 35 K. The real space pair distribution function calculations have provided a direct visualization of ASDs by means of broadening in Ni/Mn-Mn/Ni linkage. Employing the Reverse Monte Carlo approach on diffuse magnetic scattering profiles, we have observed the negative spin-spin correlation function which suggests the Ni-Ni antiferromagnetic exchange interactions ranging up to first nearest neighbor distance. These results confirm that the existence of ASDs in cation ordered host matrix leads to competing ferromagnetic-antiferromagnetic phases in a broad temperature range, which quantitatively governs the temperature dependent bulk magnetic observables of SNMO system.

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“…In the present work, we plan to investigate the EB effect in Sm 2 NiMnO 6 /BaTiO 3 /Sm 2 NiMnO 6 (SBS) heterostructure. Assuming the ideal scenario (defect free crystal structure) Sm 2 NiMnO 6 (SNMO) and BaTiO 3 (BTO) can be categorized as FM and diamagnetic systems due to Ni 2+/3+ -O-Mn 4+/3+ near linear super exchange interaction and Ti 4+ 3d 0 configuration, respectively [16,17]. However, in our previous studies we have observed that presence of defects in SNMO and BTO host matrix has huge bearings on their corresponding magnetic behaviors [17,18].…”

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confidence: 99%

“…Assuming the ideal scenario (defect free crystal structure) Sm 2 NiMnO 6 (SNMO) and BaTiO 3 (BTO) can be categorized as FM and diamagnetic systems due to Ni 2+/3+ -O-Mn 4+/3+ near linear super exchange interaction and Ti 4+ 3d 0 configuration, respectively [16,17]. However, in our previous studies we have observed that presence of defects in SNMO and BTO host matrix has huge bearings on their corresponding magnetic behaviors [17,18]. Here, we have demonstrated how defect induced alteration in electronic structure can drive unusual magnetic behavior like EB phenomenon in SBS heterostructure system.…”

mentioning

confidence: 99%

“…Following the previously optimized recipe as reported in Refs. [17,18], here we have employed 700 • C of deposition temperature (DT) and 500 mTorr of oxygen partial pressure (OPP) to grow the SBS systems. The crystal structure and phase information of the grown thin films were investigated utilizing Cu Kα (λ = 1.54 Å) radiation X-ray diffractometers (Bruker D2 Phaser, high resolution Bruker D8 Discover), and linearly polarized blue laser (∼ 473 nm) source equipped micro-Raman spectrometer (Horiba Jobin-Yvon).…”

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confidence: 99%

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Exchange bias in Sm$ _{2} $NiMnO$ _{6}$/BaTiO$ _{3}$ ferromagnetic-diamagnetic heterostructure thin films

Majumder¹,

Chowdhury²,

De³

et al. 2022

Preprint

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Exchange bias (EB) shifts are commonly reported for the ferromagnetic (FM)/antiferromagnetic (AFM) bilayer systems. While stoichiometric ordered Sm 2 NiMnO 6 (SNMO) and BaTiO 3 (BTO) are known to possesses FM and diamagnetic orderings respectively, here we have demonstrated the cooling field dependent EB and training effects in epitaxial SNMO/BTO/SNMO (SBS) heterostructure thin films. The polarized Raman spectroscopy and magnetometric studies reveal the presence of anti-site cation disorders in background of ordered lattice in SNMO layers, which introduces Ni-O-Ni or Mn-O-Mn local AFM interactions in long range Ni-O-Mn FM ordered host matrix. We have also presented growth direction manipulation of the degree of cation disorders in the SNMO system. Polarization dependent X-ray absorption measurements, duly combined with configuration interaction simulations suggest charge transfer from Ni/Mn 3d to Ti 3d orbitals through O 2p orbitals across the SNMO/BTO (SB) interfaces, which can induce magnetism in the BTO spacer layer. The observed exchange bias in SBS heterostructures is discussed considering the pinning of moments due to exchange coupling at SB (or BTO/SNMO) sandwich interface.The exchange bias (EB) phenomenon, described as the shift of isothermal magnetic hyteresis loop in the magnetic field scale, is attributed to unidirectional anisotropy effect [1,2].Ideally an antiferromagnetic (AFM) system possess equivalent energies for the two oppositely aligned magnetic sublattices. Now, the EB effect can be understood considering the exchange coupling of any one AFM sublattice spins with adjacent ferromagnetic (FM) spin arrangements, when the FM/AFM interface system (FM T C > AFM T N

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Elucidating the origin of magnetic ordering in ferroelectric BaTiO_3- d thin film via electronic structure modification

Cited by 21 publications

References 65 publications

Robust electronic and tunable magnetic states in Sm$ _{2} $NiMnO$ _{6} $ ferromagnetic insulator

Robust electronic and tunable magnetic states in Sm$ _{2} $NiMnO$ _{6} $ ferromagnetic insulator

Microscopic insights of magnetism in Sm$ _{2} $NiMnO$ _{6} $ double perovskite

Exchange bias in Sm$ _{2} $NiMnO$ _{6}$/BaTiO$ _{3}$ ferromagnetic-diamagnetic heterostructure thin films

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Elucidating the origin of magnetic ordering in ferroelectric BaTiO3- d thin film via electronic structure modification

Cited by 21 publications

References 65 publications

Robust electronic and tunable magnetic states in Sm$ _{2} $NiMnO$ _{6} $ ferromagnetic insulator

Robust electronic and tunable magnetic states in Sm$ _{2} $NiMnO$ _{6} $ ferromagnetic insulator

Microscopic insights of magnetism in Sm$ _{2} $NiMnO$ _{6} $ double perovskite

Exchange bias in Sm$ _{2} $NiMnO$ _{6}$/BaTiO$ _{3}$ ferromagnetic-diamagnetic heterostructure thin films

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Elucidating the origin of magnetic ordering in ferroelectric BaTiO_3- d thin film via electronic structure modification