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 maximum sensor sensitivity of Y2MgTiO6:Mn4+ is determined to be as high as 0.001 42 K-1 at 153 K, which demonstrates potential applications for the optical thermometry at low-temperature environments.
Abstract: Mn4+-doped Y2MgTiO6 phosphors are synthesized by the traditional solid-state method. Powder X-ray diffraction, scanning electron microscope, and energy-dispersive X-ray spectrometer are employed to...
138 citations
TL;DR: The role of antisite disorder in creating the domain structure leading to exchange bias effect is highlighted in this article, where a model based on growth of ferromagnetic domains overcoming the elastic energy of structurally pinned magnetic interfaces, which closely resembles martensitic-like transitions, is adapted to explain the observed effects.
Abstract: Exchange bias effect in the ferromagnetic double perovskite compound Y2CoMnO6, which is also a multiferroic, is reported. The exchange bias, observed below 8 K, is explained as arising due to the interface effect between the ferromagnetic and antiferromagnetic clusters created by antisite disorder in this material. Below 8 K, prominent ferromagnetic hysteresis with metamagnetic “steps” and significant coercive field, Hc ≈ 10 kOe are observed in this compound which has a Tc ≈ 75 K. A model based on growth of ferromagnetic domains overcoming the elastic energy of structurally pinned magnetic interfaces, which closely resembles martensitic-like transitions, is adapted to explain the observed effects. The role of antisite disorder in creating the domain structure leading to exchange bias effect is highlighted in the present work.
47 citations
TL;DR: In this article, the influence of rare earth site substitution on structural, transport and magnetic characteristics of polycrystalline Ln2CoMnO6 (Ln= La, Sm and Gd) has been systematically investigated in details.
41 citations
TL;DR: The role of antisite disorder in creating the domain structure leading to exchange bias effect is highlighted in this paper, where a model based on growth of ferromagnetic domains overcoming the elastic energy of structurally pinned magnetic interfaces, which closely resembles martensitic-like transitions, is adapted to explain the observed effects.
Abstract: Exchange bias effect in the ferromagnetic double perovskite compound Y$_2$CoMnO$_6$, which is also a multiferroic, is reported. The exchange bias, observed below 8~K, is explained as arising due to the interface effect between the ferromagnetic and antiferromagnetic clusters created by {\it antisite} disorder in this material. Below 8~K, prominent ferromagnetic hysteresis with metamagnetic "steps" and significant coercive field, $H_c \approx$ 10~kOe are observed in this compound which has a $T_c \approx$ 75~K. A model based on growth of ferromagnetic domains overcoming the elastic energy of structurally pinned magnetic interfaces, which closely resembles martensitic-like transitions, is adapted to explain the observed effects. The role of {\it antisite} disorder in creating the domain structure leading to exchange bias effect is highlighted in the present work.
40 citations
TL;DR: Magnetic and dielectric properties of the double perovskite Ho2NiMnO6 are reported and signs of inherent Griffiths phase pertaining to the Ni/Mn subsystem are visible.
Abstract: Magnetic and dielectric properties of the double perovskite Ho2NiMnO6 are reported. The compound is synthesized by nitrate route and is found to crystallize in monoclinic P2(1)/n space group. Lattice parameters obtained by refining powder x-ray diffraction data are; a = 5.218(2)angstrom, b = 5.543(2)angstrom, c = 7.480(3)angstrom and the monoclinic angle i beta = 90.18 degrees(4). A phase transition is observed at T-C = 86 K in the temperature-dependent magnetization curve, M(T). The inverse magnetic susceptibility, (1/chi(T)) fits reasonably well with modified Curie-Weiss law by incorporating the paramagnetic response of Ho3+. 1/chi(T) manifests as an upward deviation from ideal Curie-Weiss behaviour well above the ferromagnetic transition. Signs of inherent Griffiths phase pertaining to the Ni/Mn subsystem are visible when one subtracts the Ho3+ paramagnetic contribution from total susceptibility and does the power-law analysis. The magnetic hysteresis at 2 K gives the maximum value of magnetization M-max approximate to 15 mu(B)/f. u. at 50 kOe. Field-derivative of magnetization at 2 K shows discontinuities which indicates the existence of metamagnetic transitions in this compound. This needs to be probed further. Out of the two dielectric relaxations observed, the one at low temperature may be attributed to phononic frequencies and that at higher temperature may be due to Maxwell-Wagner relaxation. A correlation between magnetic and lattice degrees of freedom is plausible since the anomaly in dielectric constant coincides with T-C.
36 citations
References
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TL;DR: In this paper, an ordered double perovskite (Sr2FeMoO) was shown to exhibit intrinsic tunnelling-type magnetoresistance at room temperature.
Abstract: Colossal magnetoresistance—a huge decrease in resistance in response to a magnetic field—has recently been observed in manganese oxides with perovskite structure. This effect is attracting considerable interest from both fundamental and practical points of view1. In the context of using this effect in practical devices, a noteworthy feature of these materials is the high degree of spin polarization of the charge carriers, caused by the half-metallic nature of these materials20,21; this in principle allows spin-dependent carrier scattering processes, and hence the resistance, to be strongly influenced by low magnetic fields. This type of field control has been demonstrated for charge-carrier scattering at tunnelling junctions2,3 and at crystal-twin or ceramic grain boundaries4,5, although the operating temperature of such structures is still too low (⩽150 K) for most applications. Here we report a material—Sr2FeMoO6, an ordered double perovskite6—exhibiting intrinsic tunnelling-type magnetoresistance at room temperature. We explain the origin of this behaviour with electronic-structure calculations that indicate the material to be half-metallic. Our results show promise for the development of ordered perovskite magnetoresistive devices that are operable at room temperature.
2,065 citations
TL;DR: It is proposed that these effects are manifestations of thermally assisted, field-tuned resonant tunneling between quantum spin states, and attribute the observation of quantum-mechanical phenomena on a macroscopic scale to tunneling in a large (Avogadro's) number of magnetically identical molecules.
Abstract: We report the observation of steps at regular intervals of magnetic field in the hysteresis loop of a macroscopic sample of oriented M${\mathrm{n}}_{12}$${\mathrm{O}}_{12}$(C${\mathrm{H}}_{3}$COO${)}_{16}$(${\mathrm{H}}_{2}$O${)}_{4}$ crystals. The magnetic relaxation rate increases substantially when the field is tuned to a step. We propose that these effects are manifestations of thermally assisted, field-tuned resonant tunneling between quantum spin states, and attribute the observation of quantum-mechanical phenomena on a macroscopic scale to tunneling in a large (Avogadro's) number of magnetically identical molecules.
1,354 citations
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1,123 citations
622 citations
TL;DR: In this article, a combination of simulated annealing and representation analysis is used for the determination of magnetic structures from neutron diffraction data, which is a powerful new protocol for determining magnetic structures.
Abstract: The determination of magnetic structures from neutron diffraction data is often carried out by trial and error. Much time is wasted in the examination of structures that are in fact symmetry forbidden. The technique of representation analysis (RA) uses simple matrix calculations to provide model magnetic structures that can arise from a second-order phase transition, but has fallen into misuse because of its tedious nature. New Windows-based code performs these calculations automatically. Integration with refinement packages based on simulated annealing (SA) algorithms allows these models to be fitted against diffraction data. Combination of simulated annealing and representation analysis creates a powerful new protocol for the determination of magnetic structures.
450 citations