VNU-UET Repository: No conditions. Results ordered -Date Deposited. 2023-10-04T12:20:38ZEPrintshttp://eprints.uet.vnu.edu.vn/images/sitelogo.pnghttps://eprints.uet.vnu.edu.vn/eprints/2015-11-09T05:51:15Z2015-11-09T05:53:06Zhttp://eprints.uet.vnu.edu.vn/eprints/id/eprint/1264This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/12642015-11-09T05:51:15ZCritical Behavior of Y-doped Nd0.7Sr0.3MnO3 Manganites Exhibiting the Tricritical Point and Large Magnetocaloric EffectWe have determined the values of critical exponents of two polycrystalline samples (Nd1−xYx)0.7Sr0.3MnO3 (x = 0 and 0.07) from the magnetization data versus temperature and magnetic field, M(H, T), to learn about their magnetic and magnetocaloric (MC) properties. The results reveal the samples exhibiting the crossover of first-order and second-order phase transitions, where the exponent values β = 0.271 and γ = 0.922 for x = 0, and β = 0.234–0.236 and γ = 1.044–1.063 for x = 0.07 determined by using modified Arrott plots and static-scaling hypothesis are close to those expected for the tricritical mean-field theory (β = 0.25 and γ = 1.0). Particularly, the TC of x = 0 and 0.07 can be any value in the temperature ranges of 240–255 K and 170–278 K, respectively, depending on the magnitude of applied magnetic field and determination techniques. Around the TC, studying the MC effect of the samples has revealed a large magnetic-entropy change (ΔSm) up to ∼8 J/kg K for the applied field interval ΔH = 50 kOe, corresponding to refrigerant capacity values of 200–245 J/kg. These phenomena are related to the crossover nature and the persisting of FM/anti-FM interactions even above the TC, as further confirmed by electron-spin-resonance data, Curie–Weiss law-based analyses, and an exponential parameter characteristic of magnetic order n = dLn|ΔSm|/dLnH.The Long PhanT.A HoDuc Thang Phampdthang@vnu.edu.vnQ.T TranD. Thanh TranX. Phuc NguyenM. H PhanT. Huy BuiS.C. Yu2015-11-09T05:46:23Z2015-11-09T05:56:39Zhttp://eprints.uet.vnu.edu.vn/eprints/id/eprint/1265This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/12652015-11-09T05:46:23ZInhomogeneous ferromagnetism and spin-glass-like behaviour in (Nd1-xYx)0.7Sr0.3MnO3 with x = 0.21 - 0.35The magnetic properties of polycrystalline ceramic samples (Nd1-xYx)0.7Sr0.3MnO3 with x = 0.21 - 0.35 were studied by means of dc magnetization and ac susceptibility measurements. Experimental results reveal a strong decrease of the ferromagnetic (FM)-paramagnetic phase-transition temperature (TC) from 97 to 65 K as increasing x from 0.21 to 0.35, respectively. There is magnetic inhomogeneity associated with short-range FM order. Particularly, the samples undergo a spin-glass (SG) phase transition at the so-called blocking temperature (TB) below TC, which shifts toward lower temperatures with increasing the applied field, Hex; TB → Tg (the SG phase-transition temperature) as Hex → 0. The existence of the SG behavior in these samples was also confirmed by frequency (f) dependences of the ac susceptibility. For the in-phase/real component, χ'(T), it shows a frequency-dependent peak at the SG freezing temperature (Tf); Tf → Tg as f → 0. Dynamics of this process were analyzed by means of the slowing down scaling law, τ/τ0 ∝ (Tf /Tg - 1)-zv, where τ0 and zv are the characteristic time and critical exponent, respectively. Fitting the experimental Tf (f) data to the scaling law gave the results of zv = 10.1-12.3 and τ0 = 10-21-10-15s. These values are different from those expected for canonical SG systems with zv = 10 and τ0 = 10-13s, revealing the cluster-SG behavior of (Nd1-xYx)0.7Sr0.3MnO3 samples. Notably, the increase in Y content leads to the shift of τ0 and zv values toward those of canonical SG systems, which is ascribed to an expansi- n of SG clusters.T.L PhanV.D NguyenT.A HoV. Khiem NguyenD. Thanh TranX. Phuc NguyenDuc Thang Phampdthang@vnu.edu.vnS.C. Yu