DST-FIST Review:The helium liquefier at IIT Kanpur Anjan K. GuptaCoordinator, Cryogenic FacilitiesPhysics Department, IIT Kanpur6th Sept 2011

Liquid Helium UsersRecovery compressor1610LiquefierPure Gas StorageRSXCompressorImpureStorageHeGas balloonChillerStorageDewarLiquefier Overview

1610 Liquefier unit

RSX Compressor

Water Chiller unit

Recovery Compressor

Present Production Rate Liq. production: ~5800L Per cycle loss rate (past 3 months): ~25% Recovery line has been replacedPresent Status

With Liquid NitrogenWithout Liquid NitrogenPure ModeImpure ModePure ModeImpure Mode4232148.5

Liquid helium usersMPMS and PPMS facilities (Dr. Zakir Hossain)Users from Physics, Chemistry, MME, MSP, external (DMSRDE)LT-STM and transport measurements (Dr. Anjan Gupta)Various characterization facilities (Prof. Budhani)MOKE imaging setup (Dr. Satyajit Banerjee)Transport measurements (Dr. K.P. Rajeev)Low temperature Raman (Dr. Rajeev Gupta)

Instabilities in the vortex matter and peak effect phenomenon, Shyam Mohan, Jaivardhan Sinha, S. S. Banerjee, Yuri Myasoedov ; Phys. Rev. Lett. 98, 027003 (2007). In a low Tc superconductor (Tc = 7 K, NbSe2) , using detailed magnetization measurements (SQUID at IITK) and a novel way to investigate weak changes in pinning of the vortex lattice, we have uncovered various regimes of vortex pinning in the field Temperature phase diagram shown belowGiant slow velocity fluctuations in a driven vortex lattice, S. Mohan, J. Sinha, S. S. Banerjee, A. K. Sood, S. Ramakrishnan, A. K. Grover, Phys. Rev Lett.103, 167001 (2009).Corresponding to the different pinning phases found in the H-TDiagram for NbSe2 (Tc = 7K) interesting noise characteristics were found as one crosses the different Boundaries in the H-T space.T = 4.5 K,H = 1. 5 kOeT = 4.5 K,H = 7. 5 kOeT = 4.5 K,H = 13. 5 kOe

Fabricating nanostructures of magnetic and superconducting materials & investigating their propertiesRoutes to Growing nanostructures & investigating their propertiesSelf organized processes (Natural) Investigation into magnetization response of magnetic nanowires. Size range from 60 nm to 20 nm.

Low Temperature magnetization Properties measured:

Reveal significant changes in magnetic anisotropy at low temperature. Significant changes in coercive field Appearance of a novel Exchange bias effect at low T in a purely ferromagnetic system.Focussed Ion Beam (Artificial)Patterning a superconductor (NbSe2, Tc = 7K) using FIB facility at IIT KanpurHole dia 100 nmSpacing 300 nmBlind holes of depth 1 micronMagnetization response of the nanopatterned superconductor Shows interesting relaxation dynamics giving evidence of a novel Jammed vortex state due to engineered pinsGorky Shaw et al Supercon. Sc. Tech. 23, 075002 (2010)Co nanowire of dia50 nmAn example of changes in magneticAnisotropy, of nanowire at low T viz,. Squareness of the Hysteresis loop (ratio saturation to remeant moment ) as a function of T changes quite rapidly below 100K.Measurements were performedDown to 3K on SQUID

Physics of Novel Magnetic and Superconducting Materials

Zakir Hossain- Department of Physics, IIT Kanpur

Research Interest:Correlated Electron Systems- Quantum Phase Transition and Unconventional Superconductivity

(ii) Search for Novel Superconductors Interplay of superconductivity and magnetism

(iii) Phase transitions: Magnetic order, Quadrupolar order, valence transition

(iv) Properties of Materials under extreme condition of ultra low temperature, high pressure and high magnetic field.

Magnetism and Superconductivity in Eu0.5K0.5Fe2As2Parent compound EuFe2As2 exhibits two magnetic transitions at T1 (Eu-moments order) ~ 19K and T2 (Fe-moment order)~ 190 K

Suppression of Fe-moment ordering by potassium doping leads to superconductivity below 32 K.Featutes in the magnetic susceptibility are similar to that found in HoNi2B2C which show double reentrance behavior.

Coexistence of short range ordering of the Eu moments with the superconducting state below 15 K is confirmed by 151Eu Mssbauer and magnetic susceptibility.

H. S. Jeevan et.al. PRB 78, 092406 2008Anupam et.al. J. Phys. Cond. Mat (2009)Eu0.5K0.5Fe2As2

Co2FeSi Heusler alloy thin filmsMotivation: Promising candidate for spintronic application

To prepare a good quality film with high crystal and interface perfection and low disorder.Successful in preparing high quality thin film on SrTiO3(STO) using PLD.

Residual resistivity, 10K = 0.65 cm Residual resistivity ratio (RRR) = 438Such a high value of RRR and low value of residual resistivity has not been observed so far for any Heusler alloy thin films.Higher deposition temperature leads to better crystalline quality as compared to lower deposition temperatures which is in contrast to thin film grown on GaAs semiconductor.Anupam et al. to be published

Variable Temperature STM (AKG)Ref: RSI72, 3552 (2001); RSI79, 063701(2008); JPCS150, 012007 (2009)

Manganites: Effect of bandwidthPRB77, 014404 (08); APL93, 212503(08); JPCM21, 355001(09); PRB81, 155120(10)Epitaxial, PLD films On NGO or LSAT

STM/S on Graphene FETJPCM20, 225008 (2008); JJAP46, 7450 (2007); SSC (2011); APL (2011)

Weak Link -SQUIDsJAP103, 103535 (2008); Physica C 469, 268 (2009); PRB (2010)

NbN-Fe-NbN Josephson Junction arrayBose et al, APL 2009(c)(b)a) SEM micrograph of 40 nm thick Fe nano-plaquettes covered with 30 nm SC NbN. b) Schematic showing two distinct parallel conduction path for supercurrent. c) The angular dependence of magnetoresistance of Fe-NbN composite shows maximum super- current dissipation when field (3.5kG) is in the plane of the film (B | n). This is in stark contrast to pure NbN case (max. R when B || n). Upper inset shows the measurement geometry.

(a)(b)Temperature dependent R Vs. H Measurements of NbN (10 nm)/ HoNi5 (50 nm) bilayer on (100) MgO substrate. Comparison of R vs. H and M vs. H at temperature 1.7 K.NbN TC =16 K

HoNi5 TCurie = 5.5 KT Curie

0 G200 G300 G420 G1000 GSpin Reorientation in La0.67Ca0.33MnO3 thin film observed by Magnetic Force Microscopy In Plane MagnetizationOut of Plane MagnetizationInterfaceT = 110 KIn Plane Magnetic Field Singh et al. Manuscript under preparation

Temperature dependence of the real and imaginary parts of the pick-up coil voltage of two-coil mutual inductance setup And resistivity measured by four probe methodInterface Superconductivity

Laboratory for Optical Spectroscopy at Extreme Conditions of high P and low T Research Interests:Multifunctional Materials: Bulk and thin films. Theoretical and experiments on strongly correlated electron systems e.g Vanadates, ruthenates and manganites. Li ion battery materials. Alternate cathode materials. Theory and experiments. Biomaterials: Structure property correlation in doped Hydroxy-apatite.Nano-materials such as nc-silicon, nanowires etc.Diamond like carbon films and other nanostructures such as carbon nanotubes. Rajeev Gupta

Research Facility

Sample, pressure calibrant and pressure medium to be loaded in a 200 microns hole!

MicroRaman system with CCD. Low T (~ 9 K) cryostat. High T (~900 K) microscope hot stage. Miniature high pressure cell. Simultaneously measurement of transport and optical properties. Thermal measurements (DSC) upto 900 K.

Magnetization Dynamics in Antiferromagnetic NanoparticlesAging of ZFC magnetization in NiO nanoparticles at 25 K. Inset shows FC aging. Memory experiments in ZFC protocol. Difference in magnetization without and with a stop of one hour at 100 K. V. Bisht and K P Rajeev, J. Phys. : Cond. Matter 22, 016003 (2010); V. Bisht, K.P. Rajeev, and S. Banerjee. Solid State Com. (in press)Earlier related work from the group:S D Tiwari and K P Rajeev , PRB 72 104433 (2005); S D Tiwari and K P Rajeev, Thin Solid Films 505 113 (2006); S D Tiwari and K P Rajeev, PRB 77, 224430 (2008)

Non-equilibrium features in phase separated state of NdNiO3 Exhibit time dependent effects in phase separated state These time dependent effects are attributed to stochastic switching of supercooled metallic regions to stable insulating state. If we decrease the sample size such that it contains few SC regions, then we can observe the effect of switching of individual SC region. Journal of Physics: Condensed Matter 21 185402 (2009) Journal of Physics: Condensed Matter 21 485402 (2009).

Liquefier ProblemsRecovery Compressor failure: fixed under warrantyLeak in the cold box (Jan10), fixed (Feb10) under warranty and the warranty on the cold box leaks extended by two years till June12. Compressed air humidity problemsHelium purity problemsQuality of electrical powerChiller problems: ambient temperatures ~50C.Recovery line losses.LN2 problemsManpower

Financial StatusSanctioned: 360L (He plant) + 37L (comp) + 25L (Maint.)Value of the equipment: $ 812,126.11= `321 L (Dec07, 1$= ` 39.4) = `409 L (Dec08, 1$= ` 50.4)With 15% for duty and freight Expected cost= `369 Lacks (Dec07) = `471 Lacks (Dec08)Actual Freight amount was higher by ~ `45 L.Actual Expenditure: `516 Lacks Over-expenditure: `156 Lacks (IITK gives )Request from DST: 25L + 37L + 78L = `140L

COMPUTATIONAL PHYSICSINITIATIVE

Main Areas of InterestPhysics of TurbulencePhysics of Nano-clusters using Time-dependent Density Functional TheorySpin dynamics in Kondo latticeCosmology using the WMAP dataOptical properties of Meta-materialsLight diffusion in 3-D random media

M.K. HarbolaR. PrasadM.K. VermaPRINCIPAL USERS OF A HIGH PERFORMANCE COMPUTATIONAL FACILITYP. Jain S.A. RamakrishnaSinghH. Wanare

Physics of Nano-clusters Have already studied small Si and hydrogenated-Si clusters and looked at the evolution of their electronic, optical and structural properties as a function of their size. Calculational techniques: time-dependent density functional theory Car-Parinello method fast parallel computer with large memory Plan to study Mn clusters large Si-H clusters, Si nano-clusters DNA, proteins, bio-clusters

Spin dynamics in Kondo latticeInterplay of disorder and competing interactions in the carrier-induced dilute ferromagnetic state of the Kondo lattice model

Disorder is treated exactly within a numerical finite-size study

Involves diagonalization of large matrices high performance parallel computers

Cosmology using the WMAP dataCMBR Cosmic Microwave Background Radiation WMAP Wilson Microwave Anisotropy Probe IITK group has developed a novel CMBR analysis technique which does not use external input, unlike WMAP team, which uses extensive modelling of foregrounds WMAP data involves millions of pixels covering entire sky extensive numerical simulations on a high-end computer (presently analysis is being done in collaboration with IUCAA) Plans to extend analysis to study polarization data and signals for new physics, e.g. violation of statistical anisotropy violation of parity existence of light pseudoscalar particles (axions)

Optical properties of Meta-materialsOptical properties of meta materials have tremendous scientific and technological interest Study involves complex analyses of electric and magnetic fields in metallic structured materialsRequires extensive numerical calculations fast parallel computerLight diffusion in 3-D random media Development of algorithms to utilise photon-density waves to detect, localize and measure inhomogeneiteies in random media like biological tissues high performance computation Will complement experimental work already under way

Physics of Turbulence Solution of fluid dynamics equations in the presence of magnetic fields (MHD), convection, etc. Billions of coupled modes High-end computer simulations (grid size of 1283 in India against world best 40963) Use spectral method to investigate small scales Plan to study anisotropic, rotating and convective turbulence Applications in astrophysics, physics of weather and different branches of engineering

Proposed Supercomputer

High performance computation is needed to make an international impact in all these diverse research areas We propose to set up a supercomputer : 96 Itanium/Athlon processors (64-bit capability)System setting-up and management to be outsourced to the vendor Software requirements : Cluster Management and Compilers, apart from physics-specific packagesUsage : Physics Department 80% ; Others 20%Vendors include IBM, HP, Bull, HCL, etc.Budget : Rs. 85 Lakhs

******