اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدMartensite-like transition and spin-glass behavior in nanocrystalline Pr0.5Ca0.5MnO3
158
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We report on isothermal pulsed (20 ms) field magnetization, temperature dependent AC - susceptibility, and the static low magnetic field measurements carried out on 10 nm sized Pr0.5Ca0.5MnO3 nanoparticles (PCMO10). The saturation field for the magnetization of PCMO10 (~ 250 kOe) is found to be reduced in comparison with that of bulk PCMO (~300 kOe). With increasing temperature, the critical magnetic field required to melt the residual charge-ordered phase decays exponentially while the field transition range broadens, which is indicative of a Martensite-like transition. The AC - susceptibility data indicate the presence of a frequency-dependent freezing temperature, satisfying the conventional Vogel-Fulcher and power laws, pointing to the existence of a spin-glass-like disordered magnetic phase. The present results lead to a better understanding of manganite physics and might prove helpful for practical applications.
قيم البحث
اقرأ أيضاً
We report the observation of spin-glass-like behavior and strong magnetic anisotropy in extremely smooth (~1-3 AA) roughness) epitaxial (110) and (010) SrRuO3 thin films. The easy axis of magnetization is always perpendicular to the plane of the film
(unidirectional) irrespective of crystallographic orientation. An attempt has been made to understand the nature and origin of spin-glass behavior, which fits well with Heisenberg model.
The spin glass behavior of Y2Mo2O7 has puzzled physicists for nearly three decades. Free of bulk disorder within the resolution of powder diffraction methods, it is thought that this material is a rare realization of a spin glass resulting from weak
disorder such as bond disorder or local lattice distortions. Here, we report on the single crystal growth of Y2Mo2O7. Using neutron scattering, we present unique isotropic magnetic diffuse scattering arising beneath the spin glass transition despite having a well-ordered structure at the bulk level. Despite our attempts to model the diffuse scattering using a computationally exhaustive search of a class of simple spin Hamiltonians, we were unable to replicate the experimentally observed energy-integrated (diffuse) neutron scattering. A T^2-temperature dependence in the heat capacity and density functional theory calculations hint at significant frozen degeneracy in both the spin and orbital degrees of freedom resulting from spin-orbital coupling (Kugel-Khomskii type) and random fluctuations in the Mo environment at the local level.
Magneto-dielectric spectra of La0.95Ca0.05CoO3 covering the crossover of spin states reveals strong coupling of its spin and dipolar degrees of freedom. Signature of spin-state transition at 30K clearly manifests in magnetization, supported by Co L_3
,2-edge XAS data on the doped-specimen as consistent with its suppressed T_SST vs. ~150K for pure LaCoO3. Dispersive activation-step {Delta}{epsilon}(T_{omega})~O(10^2) and relaxation-peak {epsilon}(T_{omega}) reflect the allied influence of coexistent spin-states on the dielectric character. Dipolar relaxation in the LS regime below T_SST is partly segmental (VFT kinetics) featuring magnetic-field tunability, whereas in the LS/IS-spin disordered state above 30K, it is uncorrelated (Arrhenic kinetics) and almost impervious to the H-field. Kinetics-switchover defines the dipolar-glass transition temperature Tg(H), below which the magneto-thermally-activated cooperative relaxations freeze-out by the VFT temperature T_0(H). Applied H-field facilitates thermally-activated SST and accelerates the dipolar relaxations; a critical 5T field collapsing the entire kinetics into a single Arrhenic behavior. Magneto-electricity (ME) spanning sizable thermo-spectral range registers diverse signatures here in the kinetic, spectral, and field behaviors, in contrast to the static/perturbative ME observed close to the spin-ordering in typical multiferroics. Intrinsic magneto-dielectricity (50%) along with vanishing magneto-loss is obtained at (27K/50kHz)_9T. Sub-linear deviant field-hysteretic split seen in {epsilon}(H)|_>4T suggests the emergence of robust dipoles organized into nano-clusters, realized by the internally-generated high magneto-electric field. An elaborate {omega}-T multi-dispersions diagram maps the rich variety of phase/response patterns, revealing the highly-interacting magnetic and electric moments in the system.
The structural and magnetic properties of double perovskiteTb2CoMnO6 have been investigated. Electronic structure analysis by XPS study reveals the presence of mixed oxidation state (Mn4+/Mn3+ and Co2+/Co3+) of B-site ions. The dc and ac magnetizatio
n measurements reveal different interesting phases such as Griffith phase, re-entrant spin glass, metamagnetic steps, Hopkinson like peak and also unusual slow relaxation. The M-H curve indicates the presence of competing AFM/FM interactions. The disorder in Tb2CoMnO6 leads to spin frustration at low temperature giving rise to the re-entrant spin glass. Moreover, the field-dependent ac susceptibility studies unraveled the presence of Hopkinson like peak associated with the domain wall motion and the large anisotropy field. The further study yielded that the relaxation associated with this peak is unusually slow.
Famous for its spin-state puzzle, LaSrCoO$_4$ (Co$^{3+}$) is an intermediate between antiferromagnetic (AFM) La$_2$CoO$_4$ (Co$^{2+}$) and ferromagnetic (FM) Sr$_2$CoO$_4$ (Co$^{4+}$). The appearance of the Co$^{3+}$ valence state (not present in the
end compounds) is intriguing because of the spin-state transitions associated with it. In this work, we report two magnetic transitions in LaSrCoO$_4$: (i) a transition at T $=$ T$_c$ $simeq$ 225 K, from the paramagnetic state to a state with an inhomogeneous long-range ferromagnetic (FM) order wherein finite FM clusters coexist with infinite FM matrix in the percolation sense, and (ii) the transition to the cluster spin glass (CSG) state at T $=$ T$_g$ $simeq$ 8 K. Finite FM clusters (which at low temperatures give rise to the cluster spin glass state) and infinite FM matrix are formed due to the spin-spin interactions brought about by the inhomogeneously distributed Co$^{3+}$ high spin (HS) and Co$^{3+}$ low spin (LS) ions. A firm support to the presence of an unconventional (inhomogeneous) ferromagnetic order comes from the anomalous values of the critical exponents $beta$, $gamma$ and $delta$ for the spontaneous magnetization, `zero-field magnetic susceptibility and the critical M - H isotherm, while the coexistence of HS Co$^{3+}$ and LS Co$^{3+}$ ions is confirmed by the results of the extended X-ray absorption fine structure spectroscopy.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
