Arvind Maurya

Facile fabrication of lateral nanowire wrap-gate devices with improved performance

We present a simple fabrication technique for lateral nanowire wrap-gate devices with high capacitive coupling and field-effect mobility. Our process uses e-beam lithography with a single resist-spinning step and does not require chemical etching. We measure, in the temperature range 1.5–250 K, a subthreshold slope of 5–54 mV/decade and mobility of 2800–2500 cm2/Vs—significantly larger than previously reported lateral wrap-gate devices. At depletion, the barrier height due to the gated region is proportional to applied wrap-gate voltage.

EuNiGe3, an anisotropic antiferromagnet

Single crystals of EuNiGe3, crystallizing in the non-centrosymmetric BaNiSn3-type structure, were grown using In flux, enabling us to explore the anisotropic magnetic properties, which was not possible with previously reported polycrystalline samples. The EuNiGe3 single crystalline sample is found to order antiferromagnetically at 13.2 K, as revealed from the magnetic susceptibility, heat capacity and electrical resistivity data. The low temperature magnetization M (H) is distinctly different for the field parallel to the ab-plane and c-axis; the ab-plane magnetization varies almost linearly with the field before the occurrence of an induced ferromagnetic (FM) phase (spin-flip) at 6.2 Tesla. On the other hand M (H) along the c-axis is accompanied by two metamagnetic transitions followed by a spin-flip at 4.1 T. A model including anisotropic exchange and dipole-dipole interactions reproduces the main features of magnetization plots but falls short of full representation. (H,T) phase diagrams have been constructed for the field applied along the principal directions. From the (151)Eu Mössbauer spectra, we determine that the 13.2 K transition leads to an incommensurate antiferromagnetic (AFM) intermediate phase followed by a transition near 10.5 K to a commensurate AFM configuration.

Kondo Lattice and Antiferromagnetic Behavior in Quaternary CeTAl4Si2 (T = Rh, Ir) Single Crystals

We have explored in detail the anisotropic magnetic properties of CeRhAl4Si2 and CeIrAl4Si2, which undergo two antiferromagnetic transitions, at TN1 = 12.6 and 15.5 K, followed by a second transition at TN2 = 9.4 and 13.8 K, respectively, with the [001]-axis as the relatively easy axis of magnetization. The electrical resistivity at ambient and applied pressure provides evidence of Kondo interaction in both compounds, further supported by a reduced value of the entropy associated with the magnetic ordering. The Sommerfeld coefficient γ is inferred to be 195.6 and 49.4 mJ/(mol K2) for CeRhAl4Si2 and CeIrAl4Si2, respectively, classifying these materials as moderate heavy-fermion compounds. The crystal electric field energy levels are derived from the peak seen in the Schottky heat capacity. Furthermore, we have also performed electronic structure calculations by using the local spin density approximation + U [LSDA+U] approach, which provide physical insights on the observed magnetic behavior of these two co...

Anisotropic magnetic properties of EuAl2Si2

EuAl2Si2 is known to crystallize in the CaAl2Si2-type trigonal structure. We have grown single crystals of EuAl2Si2 by flux method, using Al-Si eutectic (87.8% Al) as self-flux, and investigated their anisotropic magnetic properties by means of magnetization, electrical resistivity and heat capacity in zero and applied magnetic fields, and 151Eu Mossbauer spectroscopy. Magnetic susceptibility data show an antiferromagnetic transition at TN = 33.3 K in agreement with the previously reported value on polycrystalline sample. The isothermal magnetization at 2 K measured along and perpendicular to the c-axis shows anisotropic behaviour, which is rather unexpected as Eu2+ is an S-state ion. The spin flip fields along the two directions are 2.8 and 4.8 T, respectively, while two closely spaced spin-flop transitions in the ab-plane are observed near 1.4 and 1.6 T. The electrical resistivity shows an upturn between TN and 60 K as the temperature is lowered below ~ 60 K, suggesting the presence of antiferromagnetic correlations in the paramagnetic state. Magnetoresistivity at 2 K in 14 T is nearly 1070 % for H // [0001]. The results of heat capacity and 151Eu Mossbauer spectroscopy are in conformity with a bulk transition at 33.3 K.

Anisotropic magnetic properties and crystal electric field studies on CePd2Ge2 single crystal

The anisotropic magnetic properties of the antiferromagnetic compound CePd2Ge2, crystallizing in the tetragonal crystal structure have been investigated in detail on a single crystal grown by the Czochralski method. From the electrical transport, magnetization and heat capacity data, the Néel temperature is confirmed to be 5.1 K. Anisotropic behaviour of the magnetization and resistivity is observed along the two principal crystallographic directions-namely, [100] and [001]. The isothermal magnetization measured in the magnetically ordered state at 2 K exhibits a spin reorientation at 13.5 T for the field applied along the [100] direction, whereas the magnetization is linear along the [001] direction attaining a value of 0.94 μ(B)/Ce at 14 T. The reduced value of the magnetization is attributed to the crystalline electric field (CEF) effects. A sharp jump in the specific heat at the magnetic ordering temperature is observed. After subtracting the phononic contribution, the jump in the heat capacity amounts to 12.5 J K(-1)mol(-1) which is the expected value for a spin ½ system. From the CEF analysis of the magnetization data the excited crystal field split energy levels were estimated to be at 120 K and 230 K respectively, which quantitatively explains the observed Schottky anomaly in the heat capacity. A magnetic phase diagram has been constructed based on the field dependence of magnetic susceptibility and the heat capacity data.

Exploring metamagnetism of single crystallineEuNiGe3by neutron scattering

We present here a neutron diffraction study, both in zero field and as a function of magnetic field, of the magnetic structure of the tetragonal intermetallic EuNiGe

Enhanced conduction band density of states in intermetallic EuTSi3 (T = Rh, Ir)

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Magnetic properties and complex magnetic phase diagram in non-centrosymmetric EuRhGe3 and EuIrGe3 single crystals

on a single crystalline sample. This material is known to undergo a cascade of transitions, first at 13.2 K towards an incommensurate modulated magnetic structure, then at 10.5 K to an antiferromagnetic structure. We show here that the low-temperature phase presents a spiral moment arrangement with wave vector

Crystal structure and anisotropic magnetic properties of new ferromagnetic Kondo lattice compound Ce(Cu,Al,Si)2

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Anisotropic physical properties of PrRhAl4Si2 single crystal: A non-magnetic singlet ground state compound

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