Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

We report synthesis and magnetic properties of quasi-one-dimensional spin-12 Heisenberg antiferromagnetic chain compound BaNa2Cu(VO4)2. This orthovanadate has a centrosymmetric crystal structure, C2/c, where the magnetic Cu2+ ions form spin chains. These chains are arranged in layers, with the chain direction changing by 62∘ between the two successive layers. Alternatively, the spin lattice can be viewed as anisotropic triangular layers upon taking the interchain interactions into consideration. Despite this potential structural complexity, temperature-dependent magnetic susceptibility, heat capacity, electron spin resonance intensity, and nuclear magnetic resonance (NMR) shift agree well with the uniform spin-1/2 Heisenberg chain model with an intrachain coupling of J/kB≃5.6 K. The saturation field obtained from the magnetic isotherm measurement consistently reproduces the value of J/kB. Further, the V51 NMR spin-lattice relaxation rate mimics the one-dimensional character in the intermediate temperature range, whereas magnetic long-range order sets in below TN≃0.25 K. The effective interchain coupling is estimated to be J⊥/kB≃0.1 K. The theoretical estimation of exchange couplings using band-structure calculations reciprocate our experimental findings and unambiguously establish the one-dimensional character of the compound. Finally, the spin lattice of BaNa2Cu(VO4)2 is compared with the chemically similar but not isostructural compound BaAg2Cu(VO4)2. © 2021 American Physical Society.

World University root node

Department of Physics

Physical Review B

Quasi-one-dimensional magnetism in the spin- 12 antiferromagnet BaNa2Cu(VO4)2

We report the anisotropic magnetic properties of the ternary compound ErAl2Ge2. Single crystals of this compound were grown by high temperature solution growth technique,using Al:Ge eutectic composition as flux. From the powder x-ray diffraction we confirmed that ErAl2Ge2 crystallizes in the trigonal CaAl2Si2-type crystal structure. The anisotropic magnetic properties of a single crystal were investigated by measuring the magnetic susceptibility, magnetization, heat capacity and electrical resistivity. A bulk antiferromagnetic ordering occurs around 4 K as inferred from the magnetic susceptibility and the heat capacity. The susceptibility is larger along the ab-plane and flattens out below the magnetic transition temperature and the magnetization in the ordered state increases more rapidly along the ab-plane than along the c-axis suggesting that the moments are inclined more towards the ab-plane. The magnetic susceptibility, magnetization and the 4f -derived part of the heat capacity in the paramagnetic regime analysed based on the point charge model of the crystalline electric field (CEF) indicate a relatively low CEF energy level splitting. © 2020 IOP Publishing Ltd.

Fulltext

Journal of Physics Condensed Matter

Anisotropic magnetic properties of trigonal ErAl2Ge2 single crystal

Magnetization, magnetostriction and dielectric constant measurements are performed on single crystals of quasi-one-dimensional Ising spin chain CoNb 2 O 6 at temperatures below and above the antiferromagnetic phase transition. Field-induced magnetic transitions are clearly reflected in magnetodielectric and magnetostriction data. Sharp anomalies are observed around the critical fields of antiferromagnetic to ferrimagnetic and ferrimagnetic to saturated-paramagnetic transition in both magnetodielectric and magnetostriction experiments. Detailed analysis of temperature and field dependence of dielectric constant and magnetostriction suggests that spins are coupled with lattice as well as charges in CoNb 2 O 6 . Below the antiferromagnetic transition temperature, the overall resemblance in anomalies, observed in various physical parameters such as magnetization, dielectric constant, magnetostriction and magnetic entropy change gives a deeper insight about the influence of spin configuration on these parameters in CoNb 2 O 6 . © 2019 IOP Publishing Ltd.

Spin-charge-lattice coupling in quasi-one-dimensional Ising spin chain CoNb 2 O 6

We present Se77-NMR measurements on single-crystalline FeSe under pressures up to 2 GPa. Based on the observation of the splitting and broadening of the NMR spectrum due to structural twin domains, we discovered that static, local nematic ordering exists well above the bulk nematic ordering temperature, Ts. The static, local nematic order and the low-energy stripe-type antiferromagnetic spin fluctuations, as revealed by NMR spin-lattice relaxation rate measurements, are both insensitive to pressure application. These NMR results provide clear evidence for the microscopic cooperation between magnetism and local nematicity in FeSe. © 2017 American Physical Society.

NMR evidence for static local nematicity and its cooperative interplay with low-energy magnetic fluctuations in FeSe under pressure

We have investigated the temperature and magnetic field dependence of magnetization (M), specific heat (Cp), and relative sample length change (ΔL/L0) for understanding the field-induced metamagnetic transitions in quasi-one-dimensional monoclinic (α phase) and triclinic (γ phase) CoV2O6 spin chains. With the application of external magnetic field, a sharp peak emerges in Cp(T) below TN=15K in α phase and a hump-like feature appears above TN=6.5K in γ phase due to the field-induced ferrimagnetic and ferromagnetic transitions, respectively. Strong field dependence of linear thermal expansion and large positive magnetostriction have been observed in α phase. Though magnetization data indicate strong spin-orbit coupling for both phases, other measurements show that this effect is very weak for the γ phase. © 2015 Elsevier B.V.

Journal of Magnetism and Magnetic Materials

Field induced metamagnetic transitions in quasi-one-dimensional Ising spin chain CoV2O6

We have investigated the magnetic and magnetocaloric properties of antiferromagnetic Ising spin chain CoV2O6 by magnetization and heat capacity measurements. Both monoclinic α-CoV2O6 and triclinic γ-CoV2O6 exhibit field-induced metamagnetic transitions from antiferromagnetic to ferromagnetic state via an intermediate ferrimagnetic state with 1/3 magnetization plateau. Due to the field-induced metamagnetic transitions, these systems show large conventional as well as inverse magnetocaloric effects. In α-CoV2O6, we observe field-induced complex magnetic phases and multiple magnetization plateaus below 6 K when the field is applied along c axis. Several critical temperatures and fields have been identified from the temperature and field dependence of magnetization, magnetic entropy change, and heat capacity to construct the H-T phase diagram. As compared to α-CoV2O6, γ-CoV2O6 displays a relatively simple magnetic phase diagram. Due to the large magnetic entropy change and adiabatic temperature change at low or moderate applied magnetic field, γ-CoV2O6 may be considered as a magnetic refrigerant in the low-temperature region below 20 K. © 2016 AIP Publishing LLC.

Journal of Applied Physics

Magnetic and magnetocaloric properties of quasi-one-dimensional Ising spin chain CoV2O6

APS March Meeting Abstracts 2016, C21.

Study of magnetic and magnetocaloric properties of monoclinic and triclinic spin chain CoV2O6

We have studied magnetodielectric and spin-lattice coupling in CoNb$_{2}$O$_{6}$ single crystals. Magnetostriction and magnetodielectric experiments are performed at temperatures in and above antifferomagnetic phase of quasi 1D Ising spin chain CoNb$_{2}$O$_{6}$. Field induced magnetic transitions are clearly reflected in magnetodielectric measurement as well as magnetostriction measurement also. Two sharp anomalies are found around the critical fields of antiferromagnetic to ferrimagnetic transition and ferrimagnetic to saturated paramagnetic transition in both magnetodielectric and magnetostriction experiments. High field anomaly is more pronounced for magnetodielectric response and magnetostriction also. So, in CoNb$_{2}$O$_{6}$, spins are strongly coupled with lattice as well as charges also.

arXiv preprint arXiv:1609.

Magnetodielectric and spin-lattice coupling in quasi 1D Ising spin chain CoNb$_{2}$O$_{6}$

We have investigated the temperature and magnetic field dependence of magnetization, specific heat (Cp), and relative sample length change (ΔL/L0) for understanding the field-induced spin-structural change in quasi-one-dimensional spin chain α-CoV2O6 which undergoes antiferromagnetic (AFM) transition below TN = 15 K. Analysis of Cp(T) shows that an effective S = 1/2 Ising state is realized below 20 K, though the magnetic fluctuations persist well above T N. Cp and the coefficient of linear thermal expansion (α) exhibit strong H dependence in the AFM state. We also observe a huge positive magnetostriction [ΔL(H)/L0] below 20 K which does not show any tendency of saturation up to 9 T. With increasing field, a sharp and symmetric peak emerges below TN in both Cp(T) and α(T) due to field-induced first-order ferrimagnetic/ferromagnetic- paramagnetic transitions. The large value of magnetostriction below T N suggests strong spin-lattice coupling in α-CoV 2O6. © 2013 American Chemical Society.

Journal of Physical Chemistry C

Field-induced spin-structural transition and giant magnetostriction in ising Chain α-CoV2O6

We report the existence of a Griffiths-like phase over a wide range of x due to the formation of nanosize ferromagnetic clusters in La 0.6Sr0.4Mn1-xCoxO3, the solid solution of ferromagnetic La0.6Sr0.4MnO3 and La0.6Sr0.4CoO3, from the magnetization measurements. In the studied compound, this phase arises due to the quenching of randomly distributed Co-O-Mn antiferromagnetic bonds in the ferromagnetic background. In contrary to the divalent alkaline-earth-doped manganites, the Griffiths-like phase in La0.6Sr0.4Mn1-xCo xO3 can exist entirely in the metallic state above T C (for x &lt; 0.10). Based on the present study, a magnetoelectronic phase diagram is drawn. © 2013 American Chemical Society.