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Study of Spin Glass and Cluster Ferromagnetism in Rusr2eu1.4Ce0.6Cu2o10-Δ Magneto Superconductor Anuj Kumar, R

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Study of Spin Glass and Cluster Ferromagnetism in Rusr2eu1.4Ce0.6Cu2o10-Δ Magneto Superconductor Anuj Kumar, R Study of spin glass and cluster ferromagnetism in RuSr2Eu1.4Ce0.6Cu2O10-δ magneto superconductor Anuj Kumar, R. P. Tandon, and V. P. S. Awana Citation: J. Appl. Phys. 110, 043926 (2011); doi: 10.1063/1.3626824 View online: http://dx.doi.org/10.1063/1.3626824 View Table of Contents: http://jap.aip.org/resource/1/JAPIAU/v110/i4 Published by the American Institute of Physics. Related Articles Annealing effect on the excess conductivity of Cu0.5Tl0.25M0.25Ba2Ca2Cu3O10−δ (M=K, Na, Li, Tl) superconductors J. Appl. Phys. 111, 053914 (2012) Effect of columnar grain boundaries on flux pinning in MgB2 films J. Appl. Phys. 111, 053906 (2012) The scaling analysis on effective activation energy in HgBa2Ca2Cu3O8+δ J. Appl. Phys. 111, 07D709 (2012) Magnetism and superconductivity in the Heusler alloy Pd2YbPb J. Appl. Phys. 111, 07E111 (2012) Micromagnetic analysis of the magnetization dynamics driven by the Oersted field in permalloy nanorings J. Appl. Phys. 111, 07D103 (2012) Additional information on J. Appl. Phys. Journal Homepage: http://jap.aip.org/ Journal Information: http://jap.aip.org/about/about_the_journal Top downloads: http://jap.aip.org/features/most_downloaded Information for Authors: http://jap.aip.org/authors Downloaded 12 Mar 2012 to 14.139.60.97. Redistribution subject to AIP license or copyright; see http://jap.aip.org/about/rights_and_permissions JOURNAL OF APPLIED PHYSICS 110, 043926 (2011) Study of spin glass and cluster ferromagnetism in RuSr2Eu1.4Ce0.6Cu2O10-d magneto superconductor Anuj Kumar,1,2 R. P. Tandon,2 and V. P. S. Awana1,a) 1Quantum Phenomena and Application Division, National Physical Laboratory (CSIR), Dr. K. S. Krishnan Road, New Delhi-110012, India 2Department of Physics and Astrophysics, University of Delhi, New Delhi-110007, India (Received 23 May 2011; accepted 20 July 2011; published online 29 August 2011) We report DC magnetization, detailed systematic linear and nonlinear AC magnetic susceptibility and transport for a single phase RuSr2Eu1.4Ce0.6Cu2O10-d (EuRu-1222) magneto-superconductor. The studied sample is synthesized through standard solid state reaction route, which is crystallized in single phase tetragonal structure with space group I4/mmm. DC magnetic susceptibility measurements revealed that the studied EuRu-1222 is a magneto-superconductor with Ru spins ordering at around 110 K and superconductivity in the Cu-O2 planes below 30 K. Temperature dependence of AC susceptibility with different frequency and amplitude variations confirms spin- glass behavior with cluster ferromagnetism of the system. Change in the cusp position with frequency follows the Vogel-Fulcher law, which is commonly accepted feature for a spin-glass (SG) system with ferromagnetic clusters. The third harmonic of AC susceptibility (v3) shows that the system undergoes a spin glass transition below 80 K. Superconducting transition temperature (Tc) onset and q ¼ 0 are seen at around 30 and 18 K without any applied field and the same decreases to 10 and 2 K under 130 kOe applied field. Also low fields isothermal (MH) suggests that ferromagnetic clusters are embedded in spin-glass (SG) matrix. The magnetization versus applied field (MH) loops exhibited ferromagnetic (FM) like behavior with rather small coercive fields. Detailed AC magnetic susceptibility measurements are carried out to unearth the short range magnetic correlations. These results support the spin-glass (SG) formation followed by ferromagnetic clustering effects at low temperatures. Our detailed magnetization and magneto transport results will undoubtedly contribute to current understanding of the complex magnetism of the EuRu-1222 system. VC 2011 American Institute of Physics. [doi:10.1063/1.3626824] I. INTRODUCTION resents the rare earth ion Eu or Gd).1 This is the so called Ru- 1222 type phase (the numbers reflect the number of metal The magnetic properties of rutheno-cuprates, which atoms present in their distinct crystallographic positions per belongs to the class of high temperature superconductors formula, sometimes also named the 2122-type, with RE site (HTSc), had raised significant interest in scientific commu- occupancy being listed first). Muon spin rotation (lSR) nity due to the presence of Ru ion magnetic order being experiments were performed on RuSr GdCu O (Ru1212) co-existing with superconductivity. Co-existence of super- 2 2 8Àd type phase and the presence of bulk magnetic order T ¼ 133 conductivity and magnetic order in the hybrid rutheno-cup- m K was confirmed with superconductivity at below 16 K.2,4 rates RuSr (Eu,Gd,Sm) Ce Cu O (Ru-1222) and RuSr 2 1.5 0.5 2 10-d 2 The magnetic ordering of transition metal magnetism (T ) (Eu,Gd,Sm)Cu O (Ru-1212) is interesting because the m 2 8Àd sets above the superconducting transition temperature (T ) magnetic ordering temperature is much higher (150 K) than c [e.g., for RuSr GdCu O : T 132 K and T 45 K5,6]. the superconducting transition temperature (30 K) and both 2 2 8-d m c While the co-existence of superconductivity with low temper- do co-exist in the same unit cell of these systems.1,2 A review ature antiferromagnetic (AFM) ordering in some of the rare of some earlier magnetic superconductors including RRh B 4 4 earth ions [e.g., for GdBa Cu O , T ¼ 92 K and T ¼ 2.2 and RMo S compounds (R ¼ rare earth) is presented in 2 3 7Àd c N 6 8 K7] is well known and has been investigated, the T > T is Ref. 3. Rutheno-cuprates appear to be the most challenging m c observed only for rutheno-cuprates system. Ferromagnetic- systems in term of understanding the novel phenomena of like and superconducting properties have also been reported co-existing superconductivity and ferromagnetism. More for RuSr EuCu O [(T ¼ 132 K, T 25 K),2,8 RuSr Y- than a decade is passed and scientists are yet trying to under- 2 2 8 m c 2 Cu O (T ¼ 149 K, T 39 K)9] and RuSr RECu O for stand complex magnetism of these systems.4–6 The magnetic 2 8 m c 2 2 8 RE ¼ Dy, Ho, Er.10,11 A phase separation into ferromagnetic behavior of Ru-1222 is even more complicated than Ru-1212 (FM) clusters and paramagnetic (PM) matrix followed by an phase. The first simultaneous observation of superconductiv- antiferromagnetic (AFM) transition has been assumed to ity and the Ru ion magnetic order in a rutheno-cuprate was establish magnetic correlations in these systems.12 Neutron published in 1997 for RuSr RE Ce Cu O (here RE rep- 2 1.4 0.6 2 10-d diffraction data13 did not show unique long range magnetic order, which is encountered more recently,14 primarily in a)Author to whom correspondence should be addressed. Electronic mail: Ru-1222 phase. These results are yet debated in literature. [email protected]. Also, interacting magnetic clusters in the Ru-O2 planes with 0021-8979/2011/110(4)/043926/8/$30.00 110, 043926-1 VC 2011 American Institute of Physics Downloaded 12 Mar 2012 to 14.139.60.97. Redistribution subject to AIP license or copyright; see http://jap.aip.org/about/rights_and_permissions 043926-2 Kumar, Tandon, and Awana J. Appl. Phys. 110, 043926 (2011) no long-range magnetic order, was proposed recently in of the peak is essential feature, although the exact shift is 15 Nb1ÀxRux-1222 system. The slow spin dynamics suggested different. that the FM clusters in Ru-1222 could exhibit superparamag- Keeping in view the complex magnetism of EuRu-1222, netism (SPM).12 An interesting observation of the frequency we report in this article detailed magnetization (DC/AC) and dependent peak shift of the AC susceptibility as a function of magneto-transport of a single phase EuRu-1222 compound temperature with thermoremanent magnetization (TRM) namely RuSr2Eu1.4Ce0.6Cu2O10Àd. Our results support the measurements16 revealed spin-glass (SG) behavior in spin-glass formation followed by ferromagnetic clustering Ru1222, which in a way contradicted the existence of long effects at low temperatures. range magnetic order in these systems. Spin glasses are mag- netic systems in which the magnetic moments are ‘‘in con- II. EXPERIMENTAL DETAILS flict’’ with each other due to some frozen-in structural Polycrystalline bulk sample of RuSr Eu Ce Cu O disorder. Thus no convectional long-range order (of ferro- 2 1.4 0.6 2 10Àd (EuRu-1222) was synthesized through solid state reaction magnetic or antiferromagnetic type) could be established. route from stoichiometric powders with 99.99% purity RuO , These systems exhibit a ‘‘freezing transition’’ to a state of 2 SrCO ,EuO ,CeO and CuO. These mixtures were ground new kind of order in which spins are aligned in random direc- 3 2 3 2 together in an agate mortar and calcined in air at 1020 C, tions.17 Spin-glass (SG) is simply the kinetic arrest of some 1040 Cand1060 C each for 24 hs with intermediate grind- sort of ferromagnetic and antiferromagnetic spins. One of the ings. The pressed bar shaped pellet was annealed in Oxygen characteristic phenomena observed in spin glasses systems is atmosphere at 850 C, 650 C and 450 C each for 24 hs, and the occurrence of sharp cusp in the frequency dependent AC subsequently cooled down slowly over a span of 12 hs to the susceptibility in low fields. The physics of spin glass raises room temperature. X-ray diffraction (XRD) was performed at many fundamental questions and has become one of the main room temperature in the scattering angular (2h)rangeof streams of research particularly in condensed matter physics. 20–80 in equal steps of 0.02 using Rigaku diffractometer A frequency and field dependent sharp cusp is observed in with Cu K (k ¼ 1.54A˚ ) radiation.
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