Browsing by Author "I. Panneer Muthuselvam"

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Anisotropic Magnetic Properties of Nonsymmorphic Semimetallic Single Crystal NdSbTe
(American Chemical Society, 2020) Raman Sankar; I. Panneer Muthuselvam; Karthik Rajagopal; K. Ramesh Babu; G. Senthil Murugan; Khasim Saheb Bayikadi; K. Moovendaran; Chien Ting Wu; Guang-Yu Guo
The crystal structure and magnetic, electronic, and thermal properties of a NdSbTe single crystal were examined by X-ray diffraction, magnetic and specific heat Cp(T) measurements, and density functional theory (DFT) calculations. NdSbTe undergoes an antiferromagnetic ordering at TN ≈ 2.9 K, which is obviously shown from χ(T) and Cp(T). With increasing H, a spin-flop transition is induced along the c axis, and subsequently AFM disappeared at H ≤ 0.4 T and H ≤ 2.5 T along H≈c and H≈ab, respectively. This remarkable observation shows that the ordered Nd3+ moments lie in the c axis and that there is the existence of an anisotropy scenario. The estimated magnetic anisotropy with χ≈c (0.63)/χ≈ab (0.036) is 17.5 at temperature 1.8 K. An analysis of specific heat capacity reveals the significant contribution of crystal field effects at high temperature. We carried out DFT calculations to predict the magnetic ground state and the electronic properties of NdSbTe. Our calculations revealed that the magnetic ground state is AFM with spins aligned ferromagnetically along the b axis and antiferromagnetically along the c axis. The calculated electronic band of NdSbTe exhibits a Dirac semimetal material nature. © 2020 American Chemical Society.
Anomalous spin dynamics of the S= 32 kagome ferromagnet Li9Cr3(P2 O7)3(PO4)2
(American Physical Society, 2023) G. Senthil Murugan; Chanhyeon Lee; R. Kalaivanan; I. Panneer Muthuselvam; Yugo Oshima; Kwang-Yong Choi; R. Sankar
We report the dynamical magnetic properties of the s=32 kagome ferromagnet Li9Cr3(P2O7)3(PO4)2 using magnetic susceptibility, specific heat, electron spin resonance (ESR), and nuclear magnetic resonance techniques. The magnetic susceptibility and specific heat show ferromagnetic ordering at TC=2.7 K. The in-plane ferromagnetic correlation length ζab deduced from the magnetization curves reveals that ζab increases steeply from 18.2 to 41.3 Šas the temperature is lowered from 50 K to TC, indicative of the persistence of two-dimensional magnetic correlations up to temperatures as high as ∼18TC. The ESR linewidth ΔHpp and magnetic specific heat data indicate a change in spin dynamics at about T∗≈4.4TC. Intriguingly, for temperatures below 50 K, we observe an unexpected suppression of the Li7 spin-lattice relaxation rate 1/T1. The decrease in 1/T1, which occurs well above TC, is at odds with the critical slowing down of magnetic correlations typically observed in conventional ferromagnets. This anomalous thermal evolution of spin fluctuations is interpreted in terms of the concerted interplay of flat and Dirac magnon bands inherent in kagome ferromagnets. © 2023 American Physical Society.
Cluster-glass freezing and antiferromagnetic phase transitions in corundum structure Mg3−xCoxTeO6
(Elsevier B.V., 2023) Kalimuthu Moovendaran; Raju Kalaivanan; I. Panneer Muthuselvam; N. Rajeesh Kumar; Yen-Chung Lai; Yoshiyuki iizuka; Kwang-Yong Choi; Raman Sankar
We investigate polycrystalline powder samples of the Co-substituted Mg3−xCoxTeO6 (x = 0.0–2.4) by X-ray diffraction, magnetic susceptibilities, and specific heat. The non-magnetic parent compound Mg3TeO6 crystallizes in the trigonal R3¯ space group. All Co-substituted samples have a similar crystal structure as the parent compound. The Rietveld refinements of synchrotron X-ray diffraction data reveal distorted (Mg/Co)O6 and TeO6 octahedra. Remarkably, we find the evolution of a magnetic phase from a non-magnetic ground state to an antiferromagnetic order through a cluster glass. The antiferromagnetically ordered state emerges above the percolation threshold (x ≥ 1.0), while the cluster glass state is stabilized for x = 0.8. © 2023 Elsevier B.V.
Crystal growth and magnetic properties of the coupled alternating S =1 spin chain Sr2Ni(Se O3)3
(American Physical Society, 2023) R. Madhumathy; K. Saranya; K. Moovendaran; K. Ramesh Babu; Arpita Rana; Kwang-Yong Choi; Heung-Sik Kim; Wei-Tin Chen; M. Ponmurugan; R. Sankar; I. Panneer Muthuselvam
The structural, magnetic, and thermodynamic properties of a quasi-one-dimensional (1D) S=1 alternating spin chain compound Sr2Ni(SeO3)3 are investigated by using synchrotron x-ray powder diffraction, magnetic susceptibility χ(H,T), and heat capacity CP(H,T) measurements together with density functional theory (DFT) calculations. The χ(H,T) and CP(H,T) data reveal long-range antiferromagnetic order at TN=3.4(3) K and short-range order at Tm≈7.8K. The short-range magnetic order together with 95% of spin entropy release above TN signifies the importance of 1D spin correlations persisting to ∼8TN. Theoretical DFT calculations with generalized gradient approximation determine leading exchange interactions, suggesting that interchain interactions are responsible for the observed long-range magnetic ordering. In addition, the temperature-field phase diagram of Sr2Ni(SeO3)3 is determined based on the χ(T,H) and CP(T,H) data. Interestingly, a nonmonotonic phase boundary of Tm is found for an external field applied along a hard axis. Our results suggest that the ground state and magnetic behavior of Sr2Ni(SeO3)3 rely on the interplay of single-ion anisotropy, bond alternation, and interchain interactions. © 2023 American Physical Society.
Experimental study of multiple magnetic transitions in micrometer and nano-grain sized Ni3TeO6-type oxide
(American Institute of Physics Inc., 2020) I. Panneer Muthuselvam; K. Saranya; R. Sankar; R.N. Bhowmik; L. Kavitha
We report the experimental results of dc and ac magnetic susceptibility (χdc and χac) and specific heat (CP) measurements of the powdered Ni3TeO6-type oxide. Upon decreasing the grain size from micrometer (bulk) to nanometer range, the magnetic measurements have indicated multiple transitions, viz., a cusp at paramagnetic to ferrimagnetic (FIM) transition temperature (TC) ∼78 K, an antiferromagnetic (AFM) transition temperature (TN) ∼52 K, and a re-entrant spin glass (RSG) transition at Tm2 ∼7.49 K. The ferrimagnetic transition temperature TC is found to be highly sensitive to dc magnetic fields, where superposition of a small dc field (10 Oe) in the ac susceptibility measurement or the application of a dc magnetic field of up to 100 Oe in the dc magnetic measurement is enough to suppress the observed TC at 78 K. The CP(T) measurement also revealed a RSG state at lower temperatures for the sample with nano-sized grains. The absence of any sharp peak at TC in the CP(T) curves implies the absence of a true long-range FIM spin order in the samples. The coexistence of a RSG state with multiple magnetic transitions is understood as an effect of competitive AFM and FIM phases in the Ni3TeO6-type structure. © 2020 Author(s).
High magnetic anisotropy and magnon excitations in single crystals of the double spin chain compound PbMn2Ni6Te3 O18
(American Physical Society, 2021) I. Panneer Muthuselvam; K. Saranya; Florian Büscher; Dirk Wulferding; Peter Lemmens; Wei-Tin Chen; R. Sankar
We have successfully grown single crystals of PbMn2Ni6Te3O18 and present a comprehensive study of their magnetic, thermodynamic, and Raman spectroscopic properties. PbMn2Ni6Te3O18 consists of a planar network of pairwise rotated NiO6 dimers coupled by corners. Similarities to Ni3TeO6 exist, which forms honeycomb layers. The magnetic susceptibility χ and heat capacity Cp data reveal an antiferromagnetic phase transition around 84 K, which is evidently hysteretic on warming and cooling between 94 and 40 K with a loop width of about 1.83± 0.41 K; thus the transition appears to be of first order. χ is anisotropic, with larger values for in-plane fields over the entire measured temperature range. Raman spectroscopy has been employed to investigate the lattice and magnetic excitations of the PbMn2Ni6Te3O18 from 5 to 300 K. Besides an anharmonic phonon behavior, i.e., a decay into acoustic phonons, we find a coupling to the spin system at TN=84K, as well as weak anomalies at T∗≈200K. This second characteristic temperature gives evidence for an instability of the coupled spin/lattice system, as here the phonon linewidths and intensities evidence similar behavior as at TN=84K. Furthermore, magnetic Raman scattering at 240cm-1 is used to estimate an exchange coupling of J=-86K in general agreement with the Curie-Weiss temperature. © 2021 American Physical Society.
Highly Selective Voltammetric Sensor for l -Tryptophan Using Composite-Modified Electrode Composed of CuSn(OH)6Microsphere Decorated on Reduced Graphene Oxide
(American Chemical Society, 2020) Arumugam Sangili; Venkatachalam Vinothkumar; Shen-Ming Chen; Pitchaimani Veerakumar; Chia-Wei Chang; I. Panneer Muthuselvam; King-Chuen Lin
In this study, a nanostructured CuSn(OH)6 microsphere decorated on reduced graphene oxide (CSOH/rGO) was prepared by a co-precipitation method followed by ultrasonication, which was used for the sensitive and selective determination of l-Tryptophan (l-Trp) in the presence of uric acid. Its structure and morphology were characterized by X-ray diffraction (XRD), field emission scanning/transmission electron microscopy (FE-SEM/TEM), Fourier transform infrared (FT-IR) spectroscopy, Brunauer-Emmett-Teller (BET) analysis, and X-ray photoelectron spectroscopy (XPS). Galvanostatic charge/discharge tests, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) methods have also been employed to investigate the electrochemical performance of the CSOH/rGO composite. Analytical parameters such as loading amount of catalyst, scan rate, pH value, cyclic stability, repeatability, and reproducibility were optimized. The CSOH/rGO composite shows excellent detection of l-Trp in a wide dynamic linear range (WLR) of 0.05-175.8 μM, a low limit of detection (LOD) of 2.0 nM, a limit of quantification (LOQ) of 68.9 nM, and a sensitivity of 0.21 μA μM-1 cm-2. The fabricated electrode was further used to monitor the selectivity of l-Trp in the presence of uric acid and applied to the detection of l-Trp in spiked real samples with satisfactory results. © 2020 American Chemical Society. All rights reserved.
Intriguing magnetic and electronic behaviors in La and Ru doped Sr2IrO4
(Institute of Physics, 2025) B. Dundi Sri Chandana; Jeetendra Kumar Tiwari; K. M. Saranya; Arpita Rana; G. Senthil Murugan; Dhenadhayalan Namasivayam; Kwang-yong Choi; Koppole Chandra Sekhar; P. D. Babu; Raman Sankar; I. Panneer Muthuselvam
We report a detailed experimental study of the structural, magnetic and electrical properties of La and Ru doped (Sr1−x Lax)2Ir1−xRuxO4 (x= 0.05, 0.15). X-ray diffraction analysis reveals that both samples crystallize in a tetragonal structure with a space group I41/acd without impurities. Substitution with La and Ru leads to an increase in the lattice parameter a and a decrease in c. With increasing doping concentration, the Ir-O-Ir bond angle increases while the Ir-O bond length decreases. X-ray photoelectron spectroscopy (XPS) shows that Ir has Ir3+ (5d6) and Ir4+ (5d5) charge states, where the Ir4+ charge state decreases with an increase in doping concentration. The dc magnetic susceptibility χ (T) of x= 0.05 reveals a transition from paramagnetic to weak ferromagnetic (wFM) at TC ∼ 229 K, arising from the canted antiferromagnetic (AFM) spin arrangement. The magnetic ordering temperature TC remains unaltered for higher doping, whereas the magnetic moment is significantly reduced. The analysis of real and imaginary components of ac susceptibility data, based on conventional critical slow model, frequency shift per decade and Vogel-Fulcher law, unanimously evidences the existence of reentrant spin-glass behavior (RSG), i.e. the coexistence of weak ferromagnetism and spin glass phases for the lowest doping of x= 0.05. On the other hand, for higher doping (x = 0.15) of hole and electron, the RSG phase vanishes, leaving only the wFM phase at the same temperature as observed in x = 0.05. This suggests the higher doping of La and Ru does not affect the magnetic order, but removes the disorder between FM and AFM phases. The electrical resistivity (ρ) measurement analysis reveals that both the samples show semiconducting/insulating behavior across the temperature range. The ρ of the x= 0.05 sample is lower than that of pure sample Sr2IrO4 (Bhatti et al 2015 J. Phys.:Condens. Matter 27 016005), while ρ of x = 0.15 shows two orders of magnitude larger than the x = 0.05 sample at low temperatures. The conduction mechanism of both samples is described by the 2D Mott’s variable-range hopping model. Our results demonstrate that co-doping of two cation sites generates intriguing, competing hopping and magnetic processes. © 2025 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.
Magnetic and structural dimer networks in layered K2Ni (MoO4)2
(American Physical Society, 2021) G. Senthil Murugan; K. Ramesh Babu; R. Sankar; W.T. Chen; I. Panneer Muthuselvam; Sumanta Chattopadhyay; K.-Y. Choi
The magnetic and thermodynamic properties of layered single-crystal K2Ni(MoO4)2 having both structural and magnetic dimers have been investigated. The crystal structure of K2Ni(MoO4)2 is composed of edge-sharing NiO6-octahedral pairs bridged by the MoO42- polyatomic ion groups in a plane, and the K+ ions sit in the van der Waals gap between the layers. The temperature dependence of magnetic susceptibility shows a spin-singlet ground state with an activation gap of Δ/kB≈38 K. A high-field magnetization study at T=1.5 K exhibits a half-magnetization plateau at μ0H∼25 T, corresponding to a level crossing of the singlet ground state with the lowest triplet state. Further, we have performed density functional theory calculations to determine magnetic exchange interactions. The nearest-neighbor coupling constant J1∼10 K between the Ni spins turns out to be an order of magnitude larger than all interdimer couplings. Our experimental and theoretical results suggest that K2Ni(MoO4)2 constitutes a nearly isolated two-dimensional S=1 dimer model. © 2021 American Physical Society.
Magnetic order induced by magnetic impurities in the Haldane chain compound SrNi2V2O8
(Elsevier B.V., 2024) B.D. Sri Chandana; Ambili Narayanan; K. Saranya; D. Chandrasekhar Kakarla; A. Tiwari; B. Shanmugavelu; G. Peramaiyan; G. Chandra Shekar; Kwang-Yong Choi; I. Panneer Muthuselvam
Understanding the topological properties of Haldane spin systems offers promising avenues for exploring exotic quantum phases. We investigate the impact of S = 5/2 Mn2+ impurities on the magnetic properties of SrNi2V2O8, a well-known Haldane spin gapped system. Structural characterizations of SrNi2-xMnxV2O8 (x = 0.05, 0.15, 0.30 and 0.60) through Rietveld analyses of X-ray diffraction data confirm the preservation of the I41cd space group for all studied x, along with a preferential insertion of Mn2+ ions into Ni2+ sites. Magnetic susceptibility and magnetization data unveil a magnetic transition occurring in the temperature range of T = 93–99.3 K for x = 0.05–0.60. Dielectric data evince the absence of coupling between magnetic and ferroelectric phases. Notably, the magnetic ordering temperature varies little over a wide range of Mn concentrations, while notable anomalies are observed at x = 0.15. This peculiar behavior suggests that, across low-to-high concentrations, disorder-induced magnetic moments compete with the formation of spin singlets between the nearest Mn2+ impurities, which cancel out the magnetic moments. © 2024 Elsevier B.V.
Magnetic spin order in the honeycomb structured Pb6 Co9(TeO6)5 compound
(American Physical Society, 2021) I. Panneer Muthuselvam; K. Saranya; Deepa Kasinathan; R.N. Bhowmik; R. Sankar; Namasivayam Dhenadhayalan; G.J. Shu; Wei-Tin Chen; L. Kavitha; King-Chuen Lin
We present a comprehensive experimental and theoretical study of the structural, electronic, magnetic, and thermodynamic properties of a Pb6Co9(TeO6)5 single crystal. The Pb6Co9(TeO6)5 crystal has shown a unique type of magnetic spin-lattice coupling, in which the lattice structure consists of four different Co ions sites with distorted octahedral coordinations. The x-ray photoelectron spectroscopy (XPS) results confirmed the oxidation states of Pb, Co, Te, and O elements in the sample. Moreover, XPS spectra revealed the adsorbed oxygen in the defect/vacancy sites of the lattice structure. The dc magnetization measurements exhibited a complex magnetic behavior with ferrimagnetic (FIM) transition with Curie temperature TC at ∼21 K. At lower magnetic fields H, the zero-field-cooled and field-cooled curves showed a broad hump at ∼10.8 K and a shoulder peak at ∼6.2 K, which are suppressed at higher magnetic fields. The ac susceptibility data indicated spin-glass-like features. The heat capacity CP measurements confirmed the FIM transition at TC at ∼21 K, but without any trace of additional peaks at lower temperatures. The estimated Curie-Weiss constant θCW showed a peculiar field-dependent behavior along the H∥c direction of the single crystal, where θCW is less field dependent for the H⊥c direction. A large coercivity (13 kOe) is observed at 2 K for H∥c, whereas the magnetization curve of the single crystal is dominated by an antiferromagnetic feature for H⊥c. The behaviors indicate the anisotropy nature of the exchange interactions in the compound. The local spin density approximation + U total energy calculations were performed for various collinear spin configurations of a classical Heisenberg model in order to obtain the magnetic exchange interactions Ji at different distances for different neighbors. © 2021 American Physical Society.
Magnetoelectric coupling in solid solution of Ni3-xCoxTeO6 (0 ≤ x ≤ 2.85)
(Elsevier B.V., 2025) B. D. Sri Chandana; K. Karthika; K. M. Saranya; D. Chandrasekhar Kakarla; Gunasekaran Vijayasri; Jeetendra Kumar Tiwari; Kalimuthu Moovendaran; Kwang-yong Choi; K. Chandra Shekar; Raman Sankar; I. Panneer Muthuselvam
We systematically investigate the structural, magnetic, and dielectric properties of polycrystalline samples Ni3-xCoxTeO6 (0 ≤ x ≤ 2.85). Powder X-ray diffraction reveals a structural transition from rhombohedral (R3) to monoclinic (C2/c) with increasing Co2+ substitution. The rhombohedral phase (R3) persists up to x ≤ 1.5, while x ∼ 2.55 and 2.85 adopt the monoclinic (C2/c) structure of Co3TeO6. Lattice parameters a and c increase linearly with Co2+ content, obeying Vegard's law. The DC magnetic susceptibility, χ(T), study reveals long-range antiferromagnetic ordering at TN ∼ 53 K and weak ferro/ferrimagnetic ordering at Tc ∼ 82 K for lower Co2+ substitution. As Co2+ content increases, TN shifts to ∼49 K, and Tc disappears at the critical concentration. For x ∼ 2.55, χ(T) reveals multiple magnetic transitions: short-range order at Tm ∼ 50 K, a cusp at TN1 ∼ 32 K, TN2 ∼ 28.3 K, and an abrupt change at 21.8 K. For higher substitution (x ∼ 2.85), these transitions shift slightly to lower temperatures, Tm ∼ 49.3 and TN2 ∼ 26.2, resembling Co3TeO6 except for the presence of Tm. All the measured samples show dielectric peaks near magnetic transitions, suggesting a magneto-dielectric effect. Our results demonstrate that Co substitution in Ni3TeO6 tunes both magnetic and dielectric properties across the composition range. Notably, compositions such as NCTO3 (x = 0.45) exhibit pronounced dielectric anomalies coinciding with magnetic transitions, indicating a coupling between spin and dielectric responses. This behavior points to composition-sensitive magnetoelectric interactions, underscoring the potential for tuning multiferroic functionalities within the Ni3−xCoxTeO6 solid solution. © 2025 Elsevier B.V.
Spin dynamics and 1/3 magnetization plateau in the coupled distorted diamond chain compound K2Cu3(MoO4)4
(American Physical Society, 2025) G. Senthil Murugan; Joydev Khatua; Suyoung Kim; Eundeok Mun; K. Ramesh Babu; Heung-sik Kim; C. L. Huang; Raju Kalaivanan; U. Rajesh Kumar; I. Panneer Muthuselvam; Wei Tin Chen; Sritharan Krishnamoorthi; Kwang-yong Choi; Raman Sankar
We investigate magnetic properties of the s=1/2 compound K2Cu3(MoO4)4 by combining magnetic susceptibility, magnetization, specific heat, and electron spin resonance (ESR) with density functional calculations. Its monoclinic structure features alternating Cu2+ (s=1/2) monomers and edge-shared dimers linked by MoO4 units, forming a distorted diamond chain along the a axis. Antiferromagnetic order occurs at TN=2.3 K, as evident from a λ-type anomaly in specific heat and magnetic susceptibility derivatives. Inverse magnetic susceptibility reveals coexisting ferro- and antiferromagnetic interactions. Specific heat and ESR data show two characteristic temperatures: one at 20 K, associated with spin-singlet formation in Cu2O9 dimers, and another at 3.68 K, indicating short-range correlations between dimers and monomers. Magnetization measurements reveal a metamagnetic transition at 2.6 T and a critical magnetic field μ0Hc=3.4 T, where a 1/3 magnetization plateau emerges with saturation near 0.35 μB. Low-temperature specific heat and magnetization data reveal the suppression of long-range order at μ0Hc, enabling the construction of a temperature-magnetic field phase diagram showing multiple magnetic phases near the μ0Hc. Density functional theory confirms a distorted diamond chain with J1 dimers and competing J2, J4, J3, and J5 interactions with monomer spins as an effective low-temperature spin model. © 2025 American Physical Society.
Spin-singlet ground state of the coupled Jeff = 12 alternating chain system Sr2 Co(SeO3)3
(American Physical Society, 2022) I. Panneer Muthuselvam; R. Madhumathy; K. Saranya; K. Moovendaran; Suheon Lee; Kwang-Yong Choi; Wei-Tin Chen; Chin-Wei Wang; Peng-Jen Chen; M. Ponmurugan; Min-Nan Ou; Yang-Yuan Chen; Heung-Sik Kim; R. Sankar
We report a detailed study of the structural, magnetic, thermodynamic, and electronic properties of a coupled Jeff = 12 alternating chain Sr2Co(SeO3)3 compound using magnetic susceptibility χ(T), magnetic specific heat Cm(T), magnetization, and neutron diffraction measurements along with first-principles calculations. The first-principles calculations based on the density functional theory suggest that Sr2Co(SeO3)3 forms a quasi-one-dimensional chain with bond alternation and interchain interactions. χ(T), Cm(T), and neutron powder diffraction measurements confirm that no long-range magnetic ordering occurs down to 100 mK. Instead, a maximum in χ(T) and Cm(T) and an exponential drop of χ(T) and Cp(T) as T→0 K point to a spin-singlet ground state. The analysis of χ(T) and Cm(T) based on a J1-J2 alternating Heisenberg model shows the bond alternation α=J2/J1≈0.7 and a spin gap of Δ≈3 K. Our work demonstrates that Sr2Co(SeO3)3 is a coupled alternating chain system based on spin-orbit entangled Jeff = 12. © 2022 American Physical Society.
Structural, magnetic, and electronic properties of a GdAsSe single crystal: Experimental and theoretical studies
(American Physical Society, 2024) R. Kalaivanan; Balaji Venkatesan; B. Dundi Sri Chandana; Rajesh Kumar Ulaganathan; G. Senthil Murugan; K. Moovendaran; Joydev Khatua; Li-Hsin Su; W. Zhou; Xiaofeng Xu; Chia-Seng Chang; Tien-Ming Chuang; Yoshiyuki Iizuka; I. Panneer Muthuselvam; Horng-Tay Jeng; Kwang-Yong Choi; Raman Sankar
We report high-quality single-crystal growth, x-ray diffraction, magnetic susceptibility [χ(T,H)], magnetization [M(H)], heat capacity [CP(T,H)], electrical resistivity [ρ(T,H)], and electron spin resonance (ESR) measurements of GdAsSe as functions of temperature and magnetic field. We identify an antiferromagnetic phase transition at TN∼11.9±0.2 K and construct magnetic phase diagrams for H
Thermal and field evolution of spin dynamics in the alternating Heisenberg Jeff= 12 spin chain Sr2 Co(SeO3)3
(American Physical Society, 2025) Suheon Lee; Wonjun Lee; Toni Shiroka; Kalimuthu Moovendaran; I. Panneer Muthuselvam; Raman Sankar; Eundeok Mun; Kwang-yong Choi
We present a comprehensive muon spin relaxation/rotation (μSR) study of the Co2+-based alternating Heisenberg Jeff=12 spin chain system Sr2Co(SeO3)3. Low-temperature magnetic property measurements confirm a spin-singlet ground state and identify two critical fields, HC1 and HC2. At HC1, the system evolves from the spin-singlet state to a canted antiferromagnetic phase, which persists up to HC2, where the system enters a fully polarized state. This magnetically ordered phase exists between μ0HC1c=2 T and μ0HC2c=3.05 T for μ0Hc and between μ0HC1///c=2 T and μ0HC2///c=3.6 T for H//c, reflecting the presence of anisotropy. Additionally, μSR results provide insights into the thermal and field evolution of spin dynamics, revealing a thermal crossover in spin correlations, the reopening of a spin gap due to anisotropy above HC1, and the emergence of a magnon gap above HC2. These findings imply the suppressed criticality of the canted antiferromagnetic phase by anisotropy. Our study establishes Sr2Co(SeO3)3 as a model system for investigating field-driven quantum phase transitions in one-dimensional Jeff=12 quantum spin chains with anisotropy. © 2025 American Physical Society.
Triangular Magnet Emergent from Noncentrosymmetric Sr0.94Mn0.86Te1.14O6Single Crystals
(American Chemical Society, 2022) Kalimuthu Moovendaran; Raju Kalaivanan; I. Panneer Muthuselvam; K. Ramesh Babu; Suheon Lee; C.H. Lee; Khasim Saheb Bayikadi; Namasivayam Dhenadhayalan; Wei-Tin Chen; Chin-Wei Wang; Yen-Chung Lai; Yoshiyuki Iizuka; Kwang-Yong Choi; Vladimir B. Nalbandyan; Raman Sankar
We report the successful growth of high-quality single crystals of Sr0.94Mn0.86Te1.14O6 (SMTO) using a self-flux method. The structural, electronic, and magnetic properties of SMTO are investigated by neutron powder diffraction (NPD), single-crystal X-ray diffraction (SCXRD), thermodynamic, and nuclear magnetic resonance techniques in conjunction with density functional theory calculations. NPD unambiguously determined octahedral (trigonal antiprismatic) coordination for all cations with the chiral space group P312 (no. 149), which is further confirmed by SCXRD data. The Mn and Te elements occupy distinct Wyckoff sites, and minor anti-site defects were observed in both sites. X-ray photoelectron spectroscopy reveals the existence of mixed valence states of Mn in SMTO. The magnetic susceptibility and specific heat data evidence a weak antiferromagnetic order at TN = 6.6 K. The estimated Curie-Weiss temperature θCW = -21 K indicates antiferromagnetic interaction between Mn ions. Furthermore, both the magnetic entropy and the 125Te nuclear spin-lattice relaxation rate showcase that short-range spin correlations persist well above the Néel temperature. Our work demonstrates that Sr0.94(2)Mn0.86(3)Te1.14(3)O6 single crystals realize a noncentrosymmetric triangular antiferromagnet. © 2022 American Chemical Society.