DSTFIST Review The helium liquefier at IIT Kanpur

DST-FIST Review: The helium liquefier at IIT Kanpur Anjan K. Gupta Coordinator, Cryogenic Facilities Physics Department, IIT Kanpur 6 th Sept 2011

Liquefier Overview Pure Gas Storage RSX Compressor Chiller Storage Dewar Impure Storage 1610 Liquefier Trans. Dewar Recovery compressor He Gas balloon Liquid Helium Users

1610 Liquefier unit

RSX Compressor

Water Chiller unit

Recovery Compressor

Present Production Rate With Liquid Nitrogen Without Liquid Nitrogen Pure Mode Impure Mode 42 32 14 8. 5 Present Status • Liq. production: ~5800 L • Per cycle loss rate (past 3 months): ~25% • Recovery line has been replaced

Liquid helium users • MPMS 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, Nb. Se 2) , 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 below Giant slow velocity fluctuations in a driven vortex lattice Weak Pinning Rc Thermal Fluctuations T = 4. 5 K, H = 1. 5 k. Oe T = 4. 5 K, H = 7. 5 k. Oe T = 4. 5 K, H = 13. 5 k. Oe Normal state response t (secs) Noise power Strong Pinning Correlations in voltage fluctuations , 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-T Diagram for Nb. Se 2 (Tc = 7 K) interesting noise characteristics were found as one crosses the different Boundaries in the H-T spac Normal state response f (Hz)

Fabricating nanostructures of magnetic and superconducting materials & investigating their properties Routes to Growing nanostructures & investigating their properties Self organized processes (“Natural”) • Investigation into magnetization response of magnetic nanowires. • Size range from 60 nm to 20 nm. Co nanowire of dia 50 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. An example of changes in magnetic Anisotropy, 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 100 K. Measurements were performed Down to 3 K on SQUID Focussed Ion Beam (“Artificial”) Patterning a superconductor (Nb. Se 2, Tc = 7 K) using FIB facility at IIT Kanpur Hole dia 100 nm Spacing 300 nm Blind holes of depth 1 micron Magnetization response of the nanopatterned superconductor Shows interesting relaxation dynamics giving evidence of a novel Jammed vortex state due to engineered pins Gorky Shaw et al Supercon. Sc. Tech. 23, 075002 (2010)

Physics of Novel Magnetic and Superconducting Materials Zakir Hossain- Department of Physics, IIT Kanpur Research Interest: (i) 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 Eu 0. 5 K 0. 5 Fe 2 As 2 Ø Parent compound Eu. Fe 2 As 2 exhibits two magnetic transitions at T 1 (Eumoments order) ~ 19 K and T 2 (Femoment order)~ 190 K Ø Featutes in the magnetic susceptibility are similar to that found in Ho. Ni 2 B 2 C which show double reentrance behavior. Ø Suppression of Fe-moment ordering by potassium doping leads to superconductivity below 32 K. Ø Coexistence of short range ordering of the Eu moments with the superconducting state below 15 K is confirmed by 151 Eu Mössbauer and magnetic susceptibility. H. S. Jeevan et. al. PRB 78, 092406 2008 Anupam et. al. J. Phys. Cond. Mat (2009)

Co 2 Fe. Si Heusler alloy thin films Ø Motivation: candidate application for Promising spintronic Ø To prepare a good quality film with high crystal and interface perfection and low disorder. Ø Successful in preparing high quality thin film on Sr. Ti. O 3(STO) using PLD. Ø Residual resistivity, ρ10 K = 0. 65 μΩ cm Ø Residual resistivity ratio (RRR) = 438 Ø Such a high value of RRR and low value of residual resistivity has not been observed so far for any Heusler alloy thin films. Ø Higher deposition temperature leads to better crystalline quality as compared to lower deposition temperatures which is in contrast to thin film grown on Ga. As semiconductor. Anupam et al. to be published

Variable Temperature STM (AKG) Ref: RSI 72, 3552 (2001); RSI 79, 063701(2008); JPCS 150, 012007 (2009)

Manganites: Effect of bandwidth Epitaxial, PLD films On NGO or LSAT LSMO LCMO Hwang et. al. , PRL 75, p 914 (1995) LPCMO ZBC PCMO LPCMO PRB 77, 014404 (08); APL 93, 212503(08); JPCM 21, 355001(09); PRB 81, 155120(10)

STM/S on Graphene FET A Vb Si. O 2 Doped Si Raman Transport JPCM 20, 225008 (2008); JJAP 46, 7450 (2007); SSC (2011); APL (2011) Slope: 1. 21 x 10 -3 e Vg

Weak Link μ-SQUIDs JAP 103, 103535 (2008); Physica C 469, 268 (2009); PRB (2010)

Nb. N-Fe-Nb. N Josephson Junction array (a) n [110] [100] θ B I (c) 200 nm (b) #1 i ~ 50 nm Nb. N #2 Nb. N Fe Nb. N i Nb. N a) SEM micrograph of 40 nm thick Fe nano -plaquettes covered with 30 nm SC Nb. N. b) Schematic showing two distinct parallel conduction path for supercurrent. Bose et al, APL 2009 c) The angular dependence of magnetoresistance of Fe-Nb. N composite shows maximum supercurrent dissipation when field (3. 5 k. G) is in the plane of the film (B | n). This is in stark contrast to pure Nb. N case (max. R when B || n). Upper inset shows the measurement geometry.

(a) (b) ØNb. N TC =16 K ØHo. Ni 5 TCurie = 5. 5 K T Curie<TC (a) Temperature dependent R Vs. H Measurements of Nb. N (10 nm)/ Ho. Ni 5 (50 nm) bilayer on (100) Mg. O substrate. (b) Comparison of R vs. H and M vs. H at temperature 1. 7 K. Singh et al. Manuscript submitted

Spin Reorientation in La 0. 67 Ca 0. 33 Mn. O 3 thin film observed by Magnetic Force Microscopy 0 G 420 G 200 G 300 G Out of Plane Magnetization 1000 G In Plane Magnetization Interface ØT = 110 K ØIn Plane Magnetic Field Singh et al. Manuscript under preparation

Interface Superconductivity La 1. 84 Sr 0. 16 Cu. O 4 (50 nm) La 1. 48 Nd 0. 4 Sr 0. 12 Cu. O 4 (100 nm) Substrate SLAO (001) 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 method

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

Research Facility • Micro. Raman 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. • Sample, pressure calibrant and pressure medium to be loaded in a 200 microns hole!

Magnetization Dynamics in Antiferromagnetic Nanoparticles Aging of ZFC magnetization in Ni. O 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 Nd. Ni. O 3 Exhibit time dependent effects in phase separated state v These time dependent effects are attributed to stochastic switching of supercooled metallic regions to stable insulating state. v 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. v Journal of Physics: Condensed Matter 21 185402 (2009) Journal of Physics: Condensed Matter 21 485402 (2009).

Liquefier Problems • Recovery Compressor failure: fixed under warranty • Leak in the cold box (Jan’ 10), fixed (Feb’ 10) under warranty and the warranty on “the cold box leaks” extended by two years till June’ 12. • Compressed air humidity problems • Helium purity problems • Quality of electrical power • Chiller problems: ambient temperatures ~50°C. • Recovery line losses. • LN 2 problems • Manpower

Financial Status • Sanctioned: 360 L (He plant) + 37 L (comp) + 25 L (Maint. ) • Value of the equipment: $ 812, 126. 11 = `321 L (Dec’ 07, 1$= ` 39. 4) = `409 L (Dec’ 08, 1$= ` 50. 4) • With 15% for duty and freight Expected cost = `369 Lacks (Dec’ 07) = `471 Lacks (Dec’ 08) • Actual Freight amount was higher by ~ `45 L. • Actual Expenditure: `516 Lacks • Over-expenditure: `156 Lacks (IITK gives ½) • Request from DST: 25 L + 37 L + 78 L = `140 L

COMPUTATIONAL PHYSICS INITIATIVE

Main Areas of Interest • Physics of Turbulence • Physics of Nano-clusters using Timedependent Density Functional Theory • Spin dynamics in Kondo lattice • Cosmology using the WMAP data • Optical properties of Meta-materials • Light diffusion in 3 -D random media

PRINCIPAL USERS OF A HIGH PERFORMANCE COMPUTATIONAL FACILITY M. K. Harbola P. Jain R. Prasad S. A. Ramakrishna M. K. Verma A. Singh H. Wanare

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 packages Usage : Physics Department 80% ; Others 20% Vendors include IBM, HP, Bull, HCL, etc. Budget : Rs. 85 Lakhs