Single-crystalline Gd-doped BiFeO₃ nanowires: <i>R</i>3<i>c</i>-to-<i>Pn</i>2₁<i>a</i> phase transition and enhancement in high-coercivity ferromagnetism

Patel, Sandeep Kumar Singh,Lee, Jae-Hyeok,Kim, Min-Kwan,Bhoi, Biswanath,Kim, Sang-Koog The Royal Society of Chemistry 2018 Journal of Materials Chemistry C Vol.6 No.3

<P>We fabricated single-crystalline, Gd-doped BiFeO3 (BFO) nanowires using a hydrothermal technique. X-ray diffraction (XRD) data combined with their Rietveld refinements and high-resolution transmission electron microscopy (HRTEM) revealed pure single-phase crystalline Bi1−xGdxFeO3 (<I>x</I> = 0, 0.05, 0.10) nanowires of 40-60 nm diameter and their structural transformation from the rhombohedral <I>R</I>3<I>c</I> (for <I>x</I> = 0 and 0.05) to the orthorhombic <I>Pn</I>21<I>a</I> crystal structure (for <I>x</I> = 0.10). The addition of Gd<SUP>3+</SUP> ions to the pure-phase BFO leads to remarkable changes in the structural and magnetic properties, and these effects are caused by differences in the ionic-radii and magnetic moment between the Bi<SUP>3+</SUP> and Gd<SUP>3+</SUP> ions. According to the observed magnetization-field (<I>M-H</I>) and magnetization-temperature (<I>M</I>-<I>T</I>) curves, with increasing Gd<SUP>3+</SUP> concentration, the saturation magnetization (<I>M</I>S), squareness (<I>M</I>r/<I>M</I>S), coercivity (<I>H</I>C), exchange-bias field (<I>H</I>EB) and magnetocrystalline anisotropy (<I>K</I>) increased markedly, by <I>M</I>S = 1.26 emu g<SUP>−1</SUP> (640%), <I>M</I>r/<I>M</I>S = 0.19 (20.5%), <I>H</I>C = 7788 Oe (4560%), <I>H</I>EB = 501 Oe (880%) and <I>K</I> = 1.62 × 10<SUP>5</SUP> erg cm<SUP>−3</SUP> (3500%), for <I>x</I> = 0.10 relative to the data for <I>x</I> = 0. In such Gd-doped BFO nanowire samples, spin-canted Dzyaloshinskii-Moriya interaction, remarkable enhancements in the magnetocrystalline anisotropy as well as uncompensated surface ferromagnetic spin states in the antiferromagnetic core regions were also found. Such remarkable enhancements in Gd-doped BFO nanowires might offer a variety of spintronic applications.</P>

Effects of isovalent substitution on structural and magnetic properties of nanocrystalline Y_3−xGd_xFe₅O₁₂ (0 ≤ x ≤ 3) garnets

Patel, Sandeep Kumar Singh,Lee, Jae-Hyeok,Bhoi, Biswanath,Lim, Jung Tae,Kim, Chul Sung,Kim, Sang-Koog Elsevier 2018 Journal of magnetism and magnetic materials Vol.452 No.-

<P><B>Abstract</B></P> <P>We fabricated Gd-doped Y<SUB>3</SUB>Fe<SUB>5</SUB>O<SUB>12</SUB> (YIG) nanoparticles by a modified sol–gel method. We investigated the effects of isovalent Gd<SUP>3+</SUP>-ion substitution on the structural and magnetic properties of Y<SUB>3−x</SUB>Gd<SUB>x</SUB>Fe<SUB>5</SUB>O<SUB>12</SUB> (0 ≤ x ≤ 3) nanoparticles. Isovalent Gd<SUP>3+</SUP>-ion substitution for Y<SUP>3+</SUP> leads to lattice expansion and change in the Fe(<I>a</I>)–O–Fe(<I>d</I>) bond angle. The X-ray photoemission spectroscopy and Mössbauer measurements revealed a high-spin state of Fe<SUP>3+</SUP>. The Mössbauer analysis showed an increase in the Fe<SUB>(d)</SUB> <SUP>3+</SUP>/Fe<SUB>(a)</SUB> <SUP>3+</SUP> ratio, indicating a relocation of Y<SUP>3+</SUP> ions at the dodecahedral sites and Fe<SUP>3+</SUP> ions at the octahedral sites. The magnetic properties could be explained in terms of magnetic-structural evolution with increasing Gd<SUP>3+</SUP> content. The field dependence of magnetization indicated a clear decrease of the magnetization while the magnetic anisotropy first decreases and then increases with the increase of Gd<SUP>3+</SUP> content. These Gd<SUP>3+</SUP>-ion-substituted nanocrystalline garnet ferrites are suitable for use in a variety of magneto-optical applications.</P>

Structural and Magnetic Properties of Gd-Ni-co-doped BiFeO₃ Nanoparticles

Sandeep Kumar Singh Patel,Jae-Hyeok Lee,Min-Kwan Kim,Sang-Koog Kim 한국자기학회 2019 Journal of Magnetics Vol.24 No.3

Single-phase (GdNi)x(BiFe)1-x O₃ (x = 0, 0.025, and 0.05) nanoparticles of 30-40 nm particle size on average were fabricated using a sol-gel method. Transmission electron microscopy, X-ray diffraction as well as Raman spectral measurements and analyses revealed that the (GdNi)x(BiFe)1-xO₃ nanoparticles undergo a structural transformation from the rhombohedral R3c structure (for x = 0 and 0.025) to the triclinic P1 (for x = 0.05). X-ray photoemission spectroscopy served to confirm that co-doping of Gd<SUP>3+</SUP> and Ni<SUP>2+</SUP> ions decreases oxygen-vacancy concentration, reflecting less Fe<SUP>2+</SUP> content in the co-doped samples compared with pure BiFeO₃. Magnetization hysteresis loops showed that the magnetization value for x = 0.05 at 50 kOe increases significantly to M = 5.32 emu/g at 300 K and to 14.47 emu/g at 5 K, representing 760 and 690 % enhancements relative to those for x = 0. Fitting of the Curie-Weiss law to the observed magnetization-versus-temperature curves indicated the presence of weak ferromagnetic coupling in the samples. We also noted the exchange bias effect in the nano-size particles, possibly originating from exchange coupling between surface spins of an uncompensated ferromagnetic nature and core spins of an antiferromagnetic nature. We ascribed these significant improvements in the Gd-Ni-co-doped BiFeO₃ nanoparticles’ magnetic properties to the rhombohedral R3c to triclinic P1 structural transformation, due to the samples’ particle size being smaller than the modulation length of the canted antiferromagnetic ordering of the Fe<SUP>3+</SUP> spins. These enhanced magnetic properties, notably, might prove useful for a variety of spintronic applications.

Utility of three-dimensional printing in the surgical management of intra-articular distal humerus fractures: a systematic review and meta-analysis of randomized controlled trials

Vishnu Baburaj,Sandeep Patel,Vishal Kumar,Siddhartha Sharma,Mandeep Singh Dhillon 대한견주관절의학회 2024 대한견주관절의학회지 Vol.27 No.1

Background: Clinical outcomes after fixation of distal humerus intraarticular fractures are directly related to the quality of reduction. The use of three-dimensional (3D)-printed fracture models can benefit preoperative planning to ensure good reduction. This review aims to determine if surgery performed with 3D printing assistance are faster and result in fewer complications and improved clinical outcomes than conventional methods. We also outline the benefits and drawbacks of this novel technique in surgical management of distal humerus fractures. Methods: A systematic literature search was carried out in various electronic databases. Search results were screened based on title and abstract. Data from eligible studies were extracted into spreadsheets. Meta-analysis was performed using appropriate computer software. Results: Three randomized controlled trials with 144 cases were included in the final analysis. The 3D-printed group had significantly shorter mean operating time (mean difference, 16.25 minutes; 95% confidence interval [CI], 12.74–19.76 minutes; P<0.001) and mean intraoperative blood loss (30.40 mL; 95% CI, 10.45–60.36 mL; P=0.005) compared with the conventional group. The 3D-printed group also tended to have fewer complications and a better likelihood of good or excellent outcomes as per the Mayo elbow performance score, but this did not reach statistical significance. Conclusions: Three-dimensional-printing-assisted surgery in distal humerus fractures has several benefits in reduced operating time and lower blood loss, indirectly decreasing other complications such as infection and anemia-related issues. Future good-quality studies are required to conclusively demonstrate the benefits of 3D printing in improving clinical outcomes.

Fabrication, Structure, and Magnetic Properties of Pure-Phase BiFeO3 and MnFe2O4 Nanoparticles and their Nanocomposites

Inna Yusnila Khairani,Anindityo Nugra Arifiadi,이재혁,Biswanath Bhoi,Sandeep Kumar Singh Patel,김상국 한국자기학회 2020 Journal of Magnetics Vol.25 No.2

We fabricated pure-phase BiFeO3 (BFO) and MnFe2O4 (MFO) nanoparticles as well as their nanocomposites (BMFO), and then we studied their structures and magnetic properties. Pristine BFO nanoparticles of 93.3 nm average diameter were successfully synthesized using the sol-gel method by varying the solvent condition and the precursor amount. Pristine MFO nanoparticles with a mean diameter of 70.5 nm were synthesized using the co-precipitation method entailing the optimization of the preheating and aging steps. The fabricated MFO nanoparticles showed mostly nanospheres with few nanocubes. The nanocomposite samples of 50 % MFO and 50 % BFO were fabricated through grinding and pelletization, followed by sintering under an inert atmosphere. The crystal structures of the pristine materials in the nanocomposites were well preserved. The magnetization values (Ms) of the BFO, MFO, and BMFO were 4.9, 52, and 33 emu/g, respectively. This latter Ms value was significantly higher than that of BFO, owing to the coexistence of Fe2+ and Fe3+ in its BFO phase and the incorporation of magnetic MFO. Two synthesis methods and material properties including the structural, morphological, magnetic, and oxidation states of the BFO-MFO nanocomposites were studied in order to achieve a high Ms value of 33 emu/g, which is higher than the bulk values of previously reported BFOMFO composite samples.

Structural and Magnetic Properties of Pure-Phase BiFeO₃ and MnFe₂O₄ Nanoparticles and their Nanocomposites

Inna Yusnila Khairani,Anindityo Nugra Arifiadi,Jae-Hyeok Lee,Biswanath Bhoi,Sandeep Kumar Singh Patel,Sang-koog Kim 한국자기학회 2020 한국자기학회 학술연구발표회 논문개요집 Vol.30 No.1