Structural, morphological, optical, magnetic properties and chemical state of the constituent elements of 2 at% Mn doped ZnO samples synthesized by solid state reaction and sol–gel techniques were analyzed. The role of chemical or valency state in tuning the magnetic properties has been investigated. X-ray diffractometer, scanning electron microscope, UV–visible and X-ray photoelectron spectroscopes and superconducting quantum interference device vibrating sample magnetometer (SQUID VSM) were employed for investigation. Mn incorporation in ZnO lattice has been shown by single phase wurtzite structured samples. The presence of defects particularly zinc vacancy (VZn) has been evidenced from band tailing. Solid state reaction technique derived sample exhibit strong intrinsic ferromagnetism but sol–gel sample didn’t show strong ferromagnetic (FM) ordering. Antiferromagnetic (AFM) interaction is present in both samples. The chemical state of Mn is?2 for solid state reaction technique derived sample whereas for sol–gel technique derived sample it is a mixed chemical state (exists in both +2 and +3 states). Finally, the peculiar magnetic behavior has been interpreted from the interaction between VZn and d-electrons of Mn2+ and Mn3+ states. © Springer Science+Business Media New York 2016.

ARITRA BANERJEE

Physics

SUDIPTA BANDYOPADHYAY

R KARMAKAR

S K NEOGI

N MIDYA

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Journal of Materials Science: Materials in Electronics

3 at.% Co doped sol-gel derived films were irradiated with 800 keV Ar ion beam. The studied films were un-irradiated and irradiated with fluences 5 × 10 ¹⁴ , 2.5 × 10 ¹⁵ and 10 ¹⁶ ions/cm ² . The films were characterized structurally (X-ray diffraction [XRD]), morphologically (Field Induced Scanning Electron Microscopy), optically (UV–visible, Raman spectroscopy and Photoluminescence [PL] measurements), magnetically (field and temperature dependent magnetization measurements) and electronically via local structure study (X-ray Absorption spectroscopy [XAS]). XAS data were interpreted in X-ray absorption near edge spectroscopy (XANEX) and extended X-ray absorption fine structure spectroscopy (EXAFS) measurements. XRD patterns show single-phase wurtzite structure of the films and indicate presence of defects. Raman spectra confirm single-phase structure of the films and indicate slight structural degradation in highest fluence irradiated film. The high substitutional incorporation of Co ²⁺ at Zn ²⁺ site was demonstrated from UV–visible spectra by d-d transition. The analysis of XANES and EXAFS spectra strongly reconfirms further the proper substitutional incorporation of Co ²⁺ at Zn ²⁺ site. All films are intrinsically ferromagnetic. The substantial enhancement of ferromagnetism (2.5 fold) has been observed upon irradiation (highest fluence) and it has been interpreted in terms of defects as evidenced from PL measurement. Hence the effect of Ar ion beam irradiation is highly enhanced ferromagnetism and proper Co substituted ZnO film.

Applied Surface Science

Enhanced ferromagnetism by ion irradiation for substitutionally cobalt doped ZnO films

TM0.03Zn0.97O (TM: Mn, Fe, Co and Ni) nanoparticles have been synthesized using sol-gel technique. Structural study through X-ray diffraction (XRD) has revealed that all samples, except Ni:ZnO, possess single phase wurtzite structure of ZnO, whereas in Ni:ZnO, Ni ions have mainly segregated as NiO (a secondary phase). Morphological study through Field Effect Scanning Electron Microscopy (FESEM) has confirmed the formation of nanoparticles with particle sizes in the range of 30–61 nm. X-ray absorption spectroscopy (XAS) exhibits that Co ions substitutionally replace Zn ions, Mn ions partially occupy substitutional sites and partially interstitial positions, Fe ions mainly occupy interstitial positions, whereas Ni ions mainly chemically segregate with oxygen to form NiO phase. All TM:ZnO samples show reasonable ferromagnetism (FM) up to room temperature (RT) and except for the Ni:ZnO, the observed FM seems to be intrinsic in nature. Temperature dependent magnetization (M−T) measurement of Ni:ZnO reveals a superparamagnetic behavior (with transition temperature higher than 300 K). In the regime of diluted magnetic semiconductors (DMSs) and as far as intrinsic FM is concerned, Fe:ZnO sample seems to be a good ferromagnet with appreciable saturation magnetization (MS),whereas Co:ZnO shows hard FM (with significant irreversible magnetization). The higher capability of occupying substitutional position by Co ions enhances further the utility of Co:ZnO. © 2017 Wiley-VCH Verlag GmbH &amp; Co. KGaA, Weinheim

ChemistrySelect

The Magnetic Properties of Sol-Gel Synthesized TM0.03Zn0.97O (TM: Mn, Fe, Co and Ni) Nanoparticles: Role of Different Transition Metals

Nanoparticles of Mn0.03-xCoxZn0.97O (x = 0.00, 0.01, 0.02, 0.03) have been synthesized using sol-gel technique. The wurtzite structure of ZnO has been confirmed and no impurity phase has been detected in any of the nanoparticle samples. The compositional study exhibits the presence of transition metal (TM) and further X-ray absorption near edge spectroscopy indicates quite low presence of desired Mn2+ ions whereas the presence of desired Co2+ ions is substantial. Morphological patterns have confirmed the formation of nanoparticles and supported the systematic variation of crystallite size as observed from structural study. The estimated band gap exhibits a systematic trend of red shift associated with weak quantum confinement effect and it is commensurate with the variation of particle size. Point defects particularly zinc interstitial (I-Zn) has been detected from photoluminescence (PL) measurement. Field dependent magnetization (M-H) measurement exhibits room temperature (RT) ferromagnetic (FM) ordering. The temperature dependent magnetization (M-T) measurements demonstrate the presence of simultaneous antiferromagnetic coupling which is responsible for weakening of FM ordering. Moderate temperature (350 degrees C) annealing has been found to be very effective for achieving RT FM ordering in TM doped ZnO nanoparticles and Co seems to be quite efficient than Mn so far as substitutional replacement of Zn by TM ion is concerned.

Structural, electronic, morphological, optical and magnetic properties of Mn0.03-xCoxZn0.97O (0 &lt;= x &lt;= 0.03) nanoparticles

Nanoparticles of Mn0.03–xCoxZn0.97O (x&nbsp;=&nbsp;0.00, 0.01, 0.02, 0.03) have been synthesized using sol–gel technique. The wurtzite structure of ZnO has been confirmed and no impurity phase has been detected in any of the nanoparticle samples. The compositional study exhibits the presence of transition metal (TM) and further X-ray absorption near edge spectroscopy indicates quite low presence of desired Mn2+ ions whereas the presence of desired Co2+ ions is substantial. Morphological patterns have confirmed the formation of nanoparticles and supported the systematic variation of crystallite size as observed from structural study. The estimated band gap exhibits a systematic trend of red shift associated with weak quantum confinement effect and it is commensurate with the variation of particle size. Point defects particularly zinc interstitial (IZn) has been detected from photoluminescence (PL) measurement. Field dependent magnetization (M–H) measurement exhibits room temperature (RT) ferromagnetic (FM) ordering. The temperature dependent magnetization (M–T) measurements demonstrate the presence of simultaneous antiferromagnetic coupling which is responsible for weakening of FM ordering. Moderate temperature (350&nbsp;°C) annealing has been found to be very effective for achieving RT FM ordering in TM doped ZnO nanoparticles and Co seems to be quite efficient than Mn so far as substitutional replacement of Zn by TM ion is concerned. © 2016, Springer Science+Business Media New York.

Structural, electronic, morphological, optical and magnetic properties of Mn0.03â€“xCoxZn0.97O (0Â â‰¤Â xÂ â‰¤Â 0.03) nanoparticles

The structural, morphological, optical and magnetic properties of Ar+9 implanted 5 at% Mn doped ZnO films have been investigated to detect the correlation between ferromagnetism (FM) and defect. Sol-gel derived films were implanted with fluences 0 (un-implanted), 5×1014 (low), 1015 (intermediate) and 1016 (high) ions/cm2. Rutherford back scattering (RBS), X-ray diffraction (XRD), atomic force microscope (AFM) and magnetic force microscope (MFM), UV-visible, photoluminescence and X-ray absorption spectroscopy (XAS) and superconducting quantum interference device vibrating sample magnetometer (SQUID VSM) were employed for investigation. XRD indicated single phase nature of the films. Absence of impurity phase has been confirmed from several other measurements also. Ion implantation induces a large concentration of point defects into the films as identified from optical study. All films exhibit intrinsic FM at room temperature (RT). The magnetization attains the maximum for the film implanted with fluence 1016 ions/cm2 with saturation magnetization (MS) value 0.69 emu/gm at RT. Magnetic properties of the films were interpreted using bound magnetic polaron (BMP). BMP generated from the intrinsic exchange interaction of Mn2+ ions and VZn related defects actually controls the FM. The practical utility of these films in transparent spin electronic device has also been exhibited. © 2016 Elsevier B.V. All rights reserved.

Journal of Magnetism and Magnetic Materials

Correlation between defect and magnetism of low energy Ar+9 implanted and un-implanted Zn0.95Mn0.05O thin films suitable for electronic application

Zn 0.96 Mn 0.04 O samples were synthesized by solid state reaction technique to explore their magnetic behavior. Structural, morphological and magnetic properties of the samples have been found to be modified by 50 MeV Li 3+ ion beam irradiation. The samples exhibit impurity phase and upon irradiation it disappears. Li 3+ ion irradiation has been utilized for increasing solubility limit of Mn in ZnO. Rietveld refinement analysis indicates that substitutional incorporation of Mn in the host lattice increases with irradiation. Grain size decreases with irradiation. Field dependent magnetization (M-H) measurement explicitly indicates ferromagnetic (FM) nature. It has been established from temperature dependent magnetization (M-T) measurement (500 Oe) and ac susceptibility (χ-T) measurement that ferromagnetism in the system seems to be mainly intrinsic; though superparamagnetic Mn nanoparticles also has a minor role. The analysis of M-T data at comparatively high field (5000 Oe) provides an estimation of antiferromagnetic (AFM) exchange, which acts as a reducing agent for observed magnetic moment. The value of saturation magnetization has been increased upon irradiation and is highly correlated with dissolution of impurity phase. Actually structural property has been modified with ion irradiation and this modification may cause some definite positive change in magnetic property of the sample. © 2013 Elsevier B.V. All rights reserved.

Journal of Alloys and Compounds

Structural modification by Li 3+ ion irradiation and intrinsic magnetic properties of un-irradiated and Li 3+ irradiated Zn 0.96 Mn 0.04 O samples

Structural, morphological, optical, and magnetic properties of nanocrystalline Zn 1-x Mn x O samples (x=0.01, 0.02, 0.04, 0.06, 0.08 and 0.10) prepared by the sol-gel route are studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV-visible absorption spectroscopy, Superconducting quantum interference device (SQUID) magnetometry and positron annihilation lifetime spectroscopy (PALS). XRD confirms formation of wurzite structure in all the Mn-substituted samples. A systematic increase in lattice constants and decrease in grain size have been observed with increase in manganese doping concentration up to 6 at% in the ZnO structure. An impurity phase (ZnMnO 3 ) has been detected when percentage of Mn concentration is 6 at% or higher. The optical band gap of the Mn-substituted ZnO samples decrease with increase in doping concentration of manganese whereas the width of the localized states increases. The antiferromagnetic exchange interaction is strong in the samples for 2 and 4 at% of Mn doping but it reduces when the doping level increases from 6 at% and further. Positron life time components τ 1 and τ 2 are found to decrease when concentration of the dopant exceeds 6 at%. The changes in magnetic properties as well as positron annihilation parameters at higher manganese concentration have been assigned as due to the formation of impurity phase. © 2013 Elsevier B.V.

Physical properties of antiferromagnetic Mn doped ZnO samples: Role of impurity phase

Structural and magnetic properties of 2 at% Mn doped ZnO samples with 48 and 96 hours of milling time were investigated. Structural analysis indicates typical wurtzite structure with greater Mn incorporation in case of 96 hours milled sample. The field dependent magnetization (M-H) measurements confirm ferromagnetic (FM) nature of both the samples. The tendency of variation of saturation magnetization (MS) with temperature for both samples is expected; however remanent magnetization (MR) and coercivity (HC) follows an interesting trend with temperature change. The comparatively higher values of MS, MR and HC in case of 96 hours milled sample throughout the temperature range from 5K to 300K has been correlated with greater substitutional Mn incorporation in the host ZnO lattice. © 2012 American Institute of Physics.

AIP Conference Proceedings

Role of milling time for ferromagnetic Mn doped ZnO samples

A systematic study on the modification of optical properties in mechanically milled ZnO powder has been reported here. The average grain size of the powder becomes ∼20 nm within 4 h of milling. Fluctuations of average grain size have been noticed at the initial stage of milling (within 15 min). Changes in grain morphology with milling have also been noticed in scanning electron micrographs of the samples. Room temperature optical absorption data shows a systematic red shift of absorption band edge (∼3.25 eV). The band tail parameter (extracted from the optical absorption just below the band edge) follows a simple exponential relation with the inverse of the average grain size. Significant increase of the band tail parameter has been noticed at low grain size regime. It has been analyzed that high values of band tail parameter is a representative of VZnVO type divacancy clusters. Room temperature photoluminescence spectra show decrease (except for 120 min milling) of band edge emission intensity with increase of milling time. Subsequent decrease of sub-band edge emission is, however, less prominent. The variation of PL intensity ratio (intensity at band edge peak with that at 2.3 eV) follows simple exponential decrease with the increase of band tail parameter. This indeed shows that band edge emission in ZnO is related with the overall disorder in the system, not grain size induced only. © 2011 Elsevier B.V. All rights reserved.

Journal	Data powered by TypesetJournal of Materials Science: Materials in Electronics
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ISSN	0957-4522
Open Access	No