Magnetization-steps in Y2CoMnO6 double perovskite: The role of antisite disorder
24 Sep 2014-Journal of Applied Physics (AIP Publishing LLCAIP Publishing)-Vol. 116, Iss: 12, pp 123907
TL;DR: In this paper, a paramagnetic-ferromagnetic phase transition occurs in the double perovskite Y2CoMnO6 which has been recently identified as a multiferroic.
Abstract: Antisite disorder is observed to have significant impact on the magnetic properties of the double perovskite Y2CoMnO6 which has been recently identified as a multiferroic. A paramagnetic-ferromagnetic phase transition occurs in this material at Tc ≈ 75 K. At 2 K, it displays a strong ferromagnetic hysteresis with a significant coercive field of Hc ≈ 15 kOe. Sharp steps are observed in the hysteresis curves recorded below 8 K. In the temperature range 2 K ≤ T ≤ 5 K, the hysteresis loops are anomalous as the virgin curve lies outside the main loop. The field-cooling conditions as well as the rate of field-sweep are found to influence the steps. Quantitative analysis of the neutron diffraction data shows that at room temperature, Y2CoMnO6 consists of 62% of monoclinic P21/n with nearly 70% antisite disorder and 38% Pnma. The bond valence sums indicate the presence of other valence states for Co and Mn which arise from disorder. We explain the origin of steps by using a model for pinning of magnetization at the antiphase boundaries created by antisite disorder. The steps in magnetization closely resemble the martensitic transformations found in intermetallics and display first-order characteristics as revealed in the Arrott's plots.
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TL;DR: The results based on intricate magnetic correlations and phases in Er2CoMnO6 enrich fundamental and applied research on magnetic materials through the scope of distinct magnetic characteristics in double perovskites.
Abstract: Exploring new magnetic materials is essential for finding advantageous functional properties such as magnetoresistance, magnetocaloric effect, spintronic functionality, and multiferroicity. Versatile classes of double perovskite compounds have been recently investigated because of intriguing physical properties arising from the proper combination of several magnetic ions. In this study, it is observed that the dominant ferrimagnetic phase is coexisted with a minor multiferroic phase in single-crystalline double-perovskite Er2CoMnO6. The majority portion of the ferrimagnetic order is activated by the long-range order of Er3+ moments below TEr = 10 K in addition to the ferromagnetic order of Co2+ and Mn4+ moments arising at TC = 67 K, characterized by compensated magnetization at TComp = 3.15 K. The inverted magnetic hysteresis loop observed below TComp can be described by an extended Stoner-Wohlfarth model. The additional multiferroic phase is identified by the ferroelectric polarization of 0.9 uC/m2 at 2 K. The coexisting ferrimagnetic and multiferroic phases appear to be strongly correlated in that metamagnetic and ferroelectric transitions occur simultaneously. The results based on intricate magnetic correlations and phases in Er2CoMnO6 enrich fundamental and applied research on magnetic materials through the scope of distinct magnetic characteristics in double perovskites.
23 citations
TL;DR: In this article, the Yang-Lee theory of phase transition predicts that the essential singularity of the Griffiths phase leads to very unusual critical phenomena, including a discontinuity in the magnetization isotherm at $T =T}_{C}$, which is reflected through the large value of critical exponent $\ensuremath{\delta}$.
Abstract: We have shown that ferromagnetic double perovskite ${\mathrm{Gd}}_{2}{\mathrm{CoMnO}}_{6}$ exhibits the characteristics of clustered phase, which are quite different from that of Griffiths phase observed in several perovskite compounds. The Yang-Lee theory of phase transition predicts that the essential singularity of the Griffiths phase leads to very unusual critical phenomena, including a discontinuity in the magnetization isotherm at $T={T}_{C}$, which is reflected through the large value of critical exponent $\ensuremath{\delta}$. However, the critical exponent $\ensuremath{\delta}$ for ${\mathrm{Gd}}_{2}{\mathrm{CoMnO}}_{6}$, determined from magnetization scaling analysis, comes out to be very small ($\ensuremath{\delta}=1.55\ifmmode\pm\else\textpm\fi{}0.03$). The small value of $\ensuremath{\delta}$ suggests that the continuous ordering is slow, indicating non-Griffiths-like cluster formation in the studied system, which is further supported by the evolution of susceptibility with temperature and magnetic field. Also, the observed values of all the three exponents $\ensuremath{\beta}$ ($=1.18\ifmmode\pm\else\textpm\fi{}0.06$), $\ensuremath{\gamma}$ ($=0.65\ifmmode\pm\else\textpm\fi{}0.01$), and $\ensuremath{\delta}$ are far from any existing universality class and they deviate from the mean-field values in the opposite direction to that for the conventional universality.
22 citations
Abstract: Herein we report the structure, magnetic and dielectric properties of Y2CoMnO6 (YCMO) and Y2NiMnO6 (YNMO) prepared under various conditions. On annealing in inert atmosphere, YCMO sample shows a partial decomposition while YNMO remains unaffected. Both YCMO and YNMO samples show paramagnetic to ferromagnetic transition around 80 K, but only the magnetic properties of YCMO samples depend on the preparation conditions. YCMO samples show antiferromagnetic ground state in zero field and a metamagnetic transition at relatively low field (~2 T). Differences in the annealing environment do not destroy the initial antiparallel spin order in YCMO, but affect the critical fields of metamagnetic transition. The field-dependent magnetic properties indicated soft ferromagnetic nature of YNMO samples. The dielectric measurements show distinct frequency and temperature-dependent features in YCMO samples compared to YNMO samples. A large relative permittivity with e׳ of about 104 is observed in both O2 and air-annealed YCMO samples. Multiple dielectric relaxations are observed in all the annealed YCMO and YNMO samples.
20 citations
TL;DR: In this paper, the magnetic phase transitions in a double perovskite Ho2FeCoO6 were characterized and studied through magnetization and specific heat, and the magnetic structures were elucidated through neutron powder diffraction.
Abstract: We report the experimental observation of spin reorientation in the double perovskite Ho2FeCoO6. The magnetic phase transitions in this compound are characterized and studied through magnetization and specific heat, and the magnetic structures are elucidated through neutron powder diffraction. Two magnetic phase transitions are observed in this compound-one at K, from paramagnetic to antiferromagnetic, and the other at K, from a phase with mixed magnetic structures to a single phase through a spin reorientation process. The magnetic structure in the temperature range 200–45 K is a mixed phase of the irreducible representations and , both of which are antiferromagnetic. The phase with mixed magnetic structures that exists in Ho2FeCoO6 gives rise to a large thermal hysteresis in magnetization that extends from 200 K down to the spin reorientation temperature. At T N2, the magnetic structure transforms to . Though long-range magnetic order is established in the transition metal lattice, it is seen that only short-range magnetic order prevails in the Ho3+ lattice. Our results should motivate further detailed studies on single crystals in order to explore the spin reorientation process, spin switching and the possibility of anisotropic magnetic interactions giving rise to electric polarization in Ho2FeCoO6.
20 citations
TL;DR: In this article, the double perovskite oxide Y2CoMnO6 (YCMO) was synthesized using a sol-gel method and the presence of short-range antiferromagnetic (AFM) interactions was observed in the M vs. T measurements.
17 citations
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