Structural and magnetic characterization of (Zn 1-x-y Fe x Co y )O

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Structural and magnetic characterization of (Zn1-x-yFexCoy)O Lilian Felipe Silva Tupan 1 & Marlon Ivan Valerio-Cuadros 1 & Aline Alves Oliveira 1 & Antônio Oliveira de Souza 2 & Reginaldo Barco 1 & Flávio Francisco Ivashita 1 & Edson Passamani Caetano 3 & Elisa Baggio Saitovitch 4 & Andrea Paesano Jr 1

# Springer Nature Switzerland AG 2019

Abstract In this investigation, we synthesized monophasic and nanostructured (Zn1-x-yFexCoy)O samples, with x + y = 0.05. These nanophases were characterized by X-ray diffraction, magnetization techniques, and Mössbauer spectroscopy. The analyzes revealed that doping ZnO with iron or cobalt induced a morphological change for the crystallites. The presence of cobalt in the matrix showed to enhance clustering of iron atoms and two different groups of ferric cations were identifyed diluted in the wurtzite matrix. (Zn1-x-yFexCoy)O has no magnetic order at RT but makes a transition from the paramagnetic to the spin-glass state with decreasing temperature, passing through three different magnetic regimes. The unit cell volume, remanence and coercive field of the (Zn1-x-yFexCoy)O solid system reached a maximum for co-doped samples. Keywords Fe-doped ZnO . Co-doped ZnO . DMS . Spin-glass . Mössbauer spectroscopy

1 Introduction In recent decades, the search for materials that could transport a spin-polarized electric current has attracted much attention. This interest was triggered by theoretical models that predicted that a non-magnetic semiconductor matrix doped with magnetic cations should present a ferromagnetic order at room temperature (RT) [1, 2]. Since then, these materials, named Diluted Magnetic Semiconductors (DMS), have been prepared through several combinations of hosts (e.g., III-V semiconductors) and magnetic cations (e.g., Mn, Co, and Fe), and their structure and magnetic state extensively characterized. However, most of the studied systems This article is part of the Topical Collection on Proceedings of the 16th Latin American Conference on the Applications of the Mössbauer Effect (LACAME 2018), 18-23 November 2018, Santiago de Chile, Chile Edited by Carmen Pizarro Arriagada Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10751-0191571-1) contains supplementary material, which is available to authorized users.

* Andrea Paesano, Jr [email protected] Extended author information available on the last page of the article

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only represent unclear cases of ferromagnetism at RT. In part, this absence of conclusive results is due to the possible formation of minor (magnetic) phases in the synthesis of the candidates to DMS, which could mask the true (non) magnetic nature of the prepared solid solutions. Therefore, this field demands further investigations to clarify the real phasic and magnetic states of doped semiconductors. In this investigation, we synthesized iron and cobalt co-doped ZnO by freeze-drying a mixture of Fe and Co acetates with ZnO powder, followed by heat tr

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