Unraveling intricate magnetic behavior involving negative magnetization and exchange-bias in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>ErF</mml:mi> <mml:msub> <mml:mi mathvariant="normal">e</mml:mi> <mml:mrow> <mml:mn>0.5</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">Co</mml:mi> <mml:mrow> <mml:mn>0.5</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>3</mml:mn> </mml:msub> </mml:mrow> </mml:math>

Abstract

In this paper, we present a comprehensive investigation of the distinctive magnetic properties involving the remarkable occurrences of negative magnetization (NM), exchange bias (EB), and spin reorientation (SR) in the $\mathrm{ErF}{\mathrm{e}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{O}}_{3}$ compound. The dc magnetization data, recorded in field-cooled-cooling mode, reveal a net zero magnetization at the compensation temperature $({T}_{\mathrm{COMP}})$ of 24 K, leading to the NM phenomenon in the compound. Rietveld refinement of the neutron diffraction (ND) patterns over 1.5--300 K elucidates the SR of Fe/Co spins at 100 K $({T}_{\mathrm{SR}})$ and Er magnetic ordering 4 K $({T}_{\mathrm{N}}^{\mathrm{Er}})$ resulting in ${\mathrm{\ensuremath{\Gamma}}}_{4}({G}_{x})$, ${\mathrm{\ensuremath{\Gamma}}}_{24}({G}_{z},{G}_{x})$, ${\mathrm{\ensuremath{\Gamma}}}_{2}({G}_{z})$, and ${\mathrm{\ensuremath{\Gamma}}}_{257}({G}_{z};{A}_{y}^{\mathrm{Er}}{G}_{z}^{\mathrm{Er}})$ magnetic structures at T &gt; ${T}_{\mathrm{SR}}$, ${T}_{\mathrm{SR}}\ensuremath{\ge}T{T}_{\mathrm{COMP}}$, ${T}_{\mathrm{N}}^{\mathrm{Er}}T\ensuremath{\le}{T}_{\mathrm{COMP}}$, and $T\phantom{\rule{0.16em}{0ex}}\ensuremath{\le}\phantom{\rule{0.16em}{0ex}}{T}_{\mathrm{N}}^{\mathrm{Er}}$, respectively. It is, therefore, evident that the SR of Fe/Co moments from ${\mathrm{\ensuremath{\Gamma}}}_{4}({G}_{x})$ to ${\mathrm{\ensuremath{\Gamma}}}_{2}({G}_{z})$ gets completed at the ${T}_{\mathrm{COMP}}$ of 24 K, and the Er magnetic ordering into an unusual ${\mathrm{\ensuremath{\Gamma}}}_{57}({A}_{y}^{\mathrm{Er}}{G}_{z}^{\mathrm{Er}})$ spin configuration takes place at $T\ensuremath{\le}4$ K. Anomalies in dc magnetization data (coercivity and remanent magnetization) at ${T}_{\mathrm{SR}}$, ${T}_{\mathrm{COMP}}$, and ${T}_{\mathrm{N}}^{\mathrm{Er}}$ are also reflected in the ac susceptibility data. Intriguingly, EB field $({H}_{\mathrm{EB}})$ in the compound does not change its polarity across ${T}_{\mathrm{COMP}}$ and remains positive even above ${T}_{\mathrm{COMP}}$. The observed positive ${H}_{\mathrm{EB}}$ at T &gt; ${T}_{\mathrm{COMP}}$ can be attributed to a complex spin arrangement as evident from the ND, whereas for T \ensuremath{\le} ${T}_{\mathrm{COMP}}$, positive ${H}_{\mathrm{EB}}$ has its usual explanation within the framework of the Meiklejohn-Beam model. The maximum positive ${H}_{\mathrm{EB}}$ and a broad hump in ${H}_{\mathrm{EB}}$ at ${T}_{\mathrm{COMP}}$ and ${T}_{\mathrm{SR}}$, respectively, indicate a correlation between the EB and SR in the compound. Additionally, cooling-field dependence of the EB shows a peak value \ensuremath{\sim}5 kOe; thereafter, an unusual suppression of ${H}_{\mathrm{EB}}$ up to 70 kOe cooling field is found. The observed NM below ${T}_{\mathrm{COMP}}$ is elucidated using the Cooke's model, where the polarized Er moment, under the internal magnetic field of the ordered canted antiferromagnetic Fe/Co sublattice, competes with the ferromagnetic Fe/Co moment. This results in a complete cancellation of magnetization at ${T}_{\mathrm{COMP}}$ and the emergence of NM below ${T}_{\mathrm{COMP}}$ in the compound. The specific heat data reveal a Schottky anomaly, inferring the dominant polarized nature of the Er moment below ${T}_{\mathrm{COMP}}$. In this paper, we underscore the pivotal role of Er and Fe/Co exchange coupling in shaping the intriguing and complex magnetic properties---NM and EB---of the compound. These findings highlight the potential utility of the compound in spintronic applications.

Topics & Concepts