Magnetic phase diagram and correlation between metamagnetism and superconductivity in Ru0.9Sr2YCu2.1O7.9

Abstract

Dou, S. Xue. (2013). Magnetic phase diagram and correlation between metamagnetism and superconductivity in Ru0.9Sr2YCu2.1O7.9. European Physical Journal B: Condensed Matter and Complex Systems, 86: 280. Magnetic phase diagram and correlation between metamagnetism and superconductivity in Ru0.9Sr2YCu2.1O7.9 AbstractThe magnetic superconductor Ru 0.9 Sr 2 YCu 2.1 O 7.9 (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 1.2μ B /Ru atoms with moments parallel to the c-axis is found below the magnetic transition temperature at ~140 K in the absence of magnetic field. In addition, ferromagnetism (FM) in the ab-plane develops below ~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 ~1μ 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. 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 1.2µB/Ru atoms with moments parallel to the c-axis is found below the magnetic transition temperature at ∼ 140 K in the absence of magnetic field. In addition, ferromagnetism (FM) in the ab-plane develops below ∼ 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 ∼ 1µB 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.

Magnetic phase diagrams based on static and dynamic magnetic behaviour in Ru-based superconducting ferromagnets

“…For H dc 1000 Oe, the magnetic phase diagram shows that the system below T Curie is populated with large size FM clusters aligned in the direction of the applied field, resulting in reversible behaviour of the M ZFC (T) and M FC (T) with T irr dropping almost to zero (figure 1), and M(H) curves below T Curie in figure 2 show FM-like hysteresis loops with non-zero remnant magnetization and coercive field, respectively, suggesting a field-induced FM state. The field dependent neutron powder diffraction measurements on RuSr 2 Y 1.5 Ce 0.5 Cu 2 O 10−δ reinforce these observations, but are beyond the scope of this paper and will be discussed elsewhere [32]. An important point to note here is that despite the observed field-induced FM state, magnetization does not saturate completely at high fields as expected of a FM state, either due to (i) the DM type canting of spins as previously proposed [1,12,13] or (ii) the highly anisotropic nature of the Ru-1222 system.…”