Bulk magnetization and strong intrinsic pinning in Ni-doped BaFe2As2 single crystals

TL;DR

This study investigates the magnetic properties of Ni-doped BaFe2As2 single crystals, revealing strong intrinsic pinning, high critical current densities, and distinct pinning mechanisms depending on magnetic field orientation.

Contribution

It provides detailed measurements of magnetization and pinning behavior in Ni-doped BaFe2As2 crystals, highlighting orientation-dependent pinning mechanisms and the presence of a second magnetization peak.

Findings

Critical current density exceeds 10^6 A/cm² at low temperatures.

Presence of a second magnetization peak (fish-tail effect) across a broad temperature range.

Scaling relation observed for pinning force in H//c-axis orientation, indicating normal point pinning.

Abstract

We report on measurements of isothermal irreversible magnetization loops (M(H)) of Ni-doped BaFe2-xNixAs2 single crystals with x=0.1 and x=0.14 in magnetic fields up to 14T. For both samples in field H//c-axis and H//ab-plane, critical current density calculated from M(H) curves exceeds 106 A/cm2 at low temperatures suggesting strong intrinsic pinning in our crystals. In a broad temperature range 2-17K in both field orientations nearly optimally doped single crystal displays second magnetization peak (fish-tail effect). For H//c-axis, curves of the normalized pinning force, as a function of reduced field, measured at different temperatures obey scaling relation with peak position 0.33 for BaFe1.86Ni0.14As2 crystal and 0.4 for BaFe1.9Ni0.1As2 sample indicating single normal point pinning mechanism. In striking contrast, in H//ab-plane orientation, the scaling of curves is absent.