## Abstract

The phase diagram of NdFe_{1-x}Co_{x}AsO for low cobalt substitution consists of a superconducting dome (0.05<x<0.20) with a maximum critical temperature of 16.5(2) K for x=0.12. The x=1 end member, NdCoAsO, is an itinerant ferromagnet (T_{C} =85K) with an ordered moment of 0.30 (1) µB at 15 K. Below TN =9K, Nd spin ordering results in the antiferromagnetic coupling of the existing ferromagnetic planes. Rietveld analysis reveals that the electronically important twofold tetrahedral angle increases from 111.4° to 115.7° in this series. Underdoped samples with x=0.046 (2) and x=0.065 (2) show distortions to the orthorhombic Cmma structure at 72(2) and 64(2) K, respectively. The temperature dependences of the critical fields H_{c2} (T) near Tc are linear with almost identical slopes of 2.3 (1) T K^{-1} for x=0.065 (2), x=0.118 (2), and x=0.172 (2). The estimated critical field H_{c2} (0) and correlation length for optimally doped samples are 26(1) T and 36 (1) Å. A comparison of the maximum reported critical temperatures of well-characterized cobalt-doped 122- and 1111-type superconductors is presented. © 2010 The American Physical Society.

Original language | English |
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Article number | 064511 |

Journal | Physical Review B: Condensed Matter and Materials Physics |

Volume | 81 |

Issue number | 6 |

DOIs | |

Publication status | Published - 19 Feb 2010 |