Browsing by Author "Nigam, R"

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    Magnetic field dependent neutron powder diffraction studies of Ru0.9Sr2YCu2.1O7.9
    (American Institute of Physics, 2010-05-01) Nigam, R; Pan, AV; Dou, SX; Kennedy, SJ; Studer, AJ; Stuesser, N
    Temperature and magnetic field dependent neutron diffraction has been used to study the magnetic order in Ru0.9Sr2YCu2.1O7.9. The appearance of (1/2, 1/2, 1/2), (1/2, 1/2, 3/2), and (1/2, 1/2, 5/2) peaks below TM = 140 K manifests the antiferromagnetic order. Neutron diffraction patterns measured in applied magnetic fields from 0 to 6 T show the destruction of the antiferromagnetic order with increasing field. There is no evidence of spontaneous or field-induced long range ferromagnetic order. This latter result contradicts the vast majority of other experimental observations for this system. © 2010, American Institute of Physics
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    Magnetic phase diagram and correlation between metamagnetism and superconductivity in Ru0.9Sr2YCu2.1O7.9
    (Springer, 2013-06-01) Nigam, R; Kennedy, SJ; Pan, AV; Dou, SX
    The magnetic superconductor Ru0.9Sr2YCu2.1O7.9 (Ru-1212Y) has been investigated using neutron diffraction under variable temperature and magnetic field. With the complementary information from magnetization measurements, we propose a magnetic phase diagram T-H for the Ru-1212 system. Uniaxial antiferromagnetic (AFM) order of 1.2 mu(B)/Ru atoms with moments parallel to the c-axis is found below the magnetic transition temperature at similar to 140 K in the absence of magnetic field. In addition, ferromagnetism (FM) in the ab-plane develops below similar to 120 K, but is suppressed at lower temperature by superconducting correlations. Externally applied magnetic fields cause Ru-moments to realign from the c-axis to the ab-plane, i.e. along the < 1, 1, 0 > direction, and induce ferromagnetism in the plane with similar to 1 mu(B) at 60 kOe. These observations of the weak ferromagnetism suppressed by superconductivity and the field-induced metamagnetic transition between AFM and FM demonstrate not only competing orders of superconductivity and magnetism, but also suggest a certain vortex dynamics contributing to these magnetic transitions. © 2013, Springer.