Materials with strongly coupled magnetic and electronic degrees of freedom provide new possibilities for practical applications.In this paper,we have investigated the structure,magnetic property,and magnetodielectric(...Materials with strongly coupled magnetic and electronic degrees of freedom provide new possibilities for practical applications.In this paper,we have investigated the structure,magnetic property,and magnetodielectric(MD) effect in Ho_(2)Cu_(2)O_(5) and Yb_(2)Cu_(2)O_(5) poly crystalline samples,which possess a non-centrosymmetric polar structure with space group Pna2_(1).In Ho_(2)Cu_(2)O_(5),Ho^(3+) and Cu^(2+) sublattices order simultaneously,exhibiting a typical paramagnetic to antiferromagnetic transition at 13.1 K.While for Yb_(2)Cu_(2)O_(5),two magnetic transitions which originate from the orderings of Yb^(3+)(7.8 K) and Cu^(2+)(13.5 K) sublattices are observed.A magnetic field induced metamagnetic transition is obtained in these two cuprates below Neel temperature(T_(N)).By means of dielectric measurement,distinct MD effect is demonstrated by the dielectric anomaly at T_(N.)Meanwhile,the MD effect is found to be directly related to the metamagnetic transition.Due to the specific spin configuration and different spin evolution in the magnetic field,a positive MD effect is formed in Ho_(2)Cu_(2)O_(5),and a negative one is observed in Yb_(2)Cu_(2)O_(5).The spontaneous dielectric anomaly at T_(N) is regarded as arising from the shifts in optical phonon frequencies,and the magnetoelectric coupling is used to interpret the magnetic field induced MD effect.Moreover,an H-T phase diagram is constructed for Ho_(2)Cu_(2)O_(5) and Yb_(2)Cu_(2)O_(5) based on the results of isothermal magnetic and dielectric hysteresis loops.展开更多
Different magnetodielectric effects were observed in Bi1-xGdxFeOa ceramics depending on gadolinium content. A positive one was observed in the samples with x ≤ 0.10 at 295 K and 16 K, and a negative one in the sample...Different magnetodielectric effects were observed in Bi1-xGdxFeOa ceramics depending on gadolinium content. A positive one was observed in the samples with x ≤ 0.10 at 295 K and 16 K, and a negative one in the sample with x = 0.4 at 16 K. Structure analysis by x-ray diffraction （XRD） reveals that the samples crystallize in the R3c structure （ferroelectrics） for x 〈 0.08 and in the Pbnm structure （paraelectrics） for x ≥ 0.3 at room temperature. Temperaturedependent dielectric response and x-ray diffraction confirm the occurrence of a structural transition in the Pbnm phase at low temperature for the samples with x ≤0.4. While the positive magnetodielectric effects can be attributed to a coupling of magnetic and crystallographic structures of the R3c phase, the observed negative magnetodielectric effect in the Pbnm phase can be associated with a low-temperature modification of the Pbnm structure. The observed dualsigned magnetodielectric effects suggest that the Bi1-xGdxFeO3 oxides are a good prototype for understanding the magnetodielectric coupling mechanism in this kind of materials.展开更多
Lead-free multiferroic composites of 1−x(K_(0.5)Na_(0.5)NbO_(3−x))(Co_(0.6)Zn_(0.4))(Fe_(1.7)Mn_(0.3))O_(4)(KNN-CZFMO),where x=0.0,0.1,0.2,0.3,0.4,0.5 and 1.0,have been investigated for their structural,morphological,...Lead-free multiferroic composites of 1−x(K_(0.5)Na_(0.5)NbO_(3−x))(Co_(0.6)Zn_(0.4))(Fe_(1.7)Mn_(0.3))O_(4)(KNN-CZFMO),where x=0.0,0.1,0.2,0.3,0.4,0.5 and 1.0,have been investigated for their structural,morphological,electrical,magnetic,dielectric and magneto-dielectric properties.Presence of KNN and CZFMO crystal structure in each composite has been confirmed from X-ray diffrac-tion analysis(XRD).Cuboidal-shaped grains of KNN and spherical-shaped grains of CZFMO have been observed by scanning electron microscopy(SEM).The room temperature ferroelectric behavior as confirmed by polarization versus electric field(P-E)hysteresis loops has been found to be decreasing with increasing CZFMO concentration.Increasing magnetic ordering with the increase in CZFMO concentration in the prepared composites has been observed by magnetization versus magnetic field(M-H)hysteresis loops.The electrical conductivity of composites has been studied using Jonscher’s universal power law.The room temperature dielectric constant(ε′)and dielectric loss(tanδ)have been observed to decrease with the increase in the frequency of the applied external electric field.The dielectric relaxation behavior has been observed using curve fitting analysis via the Havriliak-Negami relaxation model.Maximum value of the magnetodielectric(MD)effect~−11%at a frequency of 1 kHz with the applied magnetic field of 1 T has been achieved for 0.9 KNN−0.1 CZFMO(x=0.1)composite in the present research work.展开更多
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.11704091)the Open Project of Guangxi Key Laboratory of Nuclear Physics and Nuclear Technology(Grant No.NLK2021-10)the Open Project of Key Laboratory of Novel Materials for Sensor of Zhejiang Province,China(Grant No.ZJKLNMS2021010)。
文摘Materials with strongly coupled magnetic and electronic degrees of freedom provide new possibilities for practical applications.In this paper,we have investigated the structure,magnetic property,and magnetodielectric(MD) effect in Ho_(2)Cu_(2)O_(5) and Yb_(2)Cu_(2)O_(5) poly crystalline samples,which possess a non-centrosymmetric polar structure with space group Pna2_(1).In Ho_(2)Cu_(2)O_(5),Ho^(3+) and Cu^(2+) sublattices order simultaneously,exhibiting a typical paramagnetic to antiferromagnetic transition at 13.1 K.While for Yb_(2)Cu_(2)O_(5),two magnetic transitions which originate from the orderings of Yb^(3+)(7.8 K) and Cu^(2+)(13.5 K) sublattices are observed.A magnetic field induced metamagnetic transition is obtained in these two cuprates below Neel temperature(T_(N)).By means of dielectric measurement,distinct MD effect is demonstrated by the dielectric anomaly at T_(N.)Meanwhile,the MD effect is found to be directly related to the metamagnetic transition.Due to the specific spin configuration and different spin evolution in the magnetic field,a positive MD effect is formed in Ho_(2)Cu_(2)O_(5),and a negative one is observed in Yb_(2)Cu_(2)O_(5).The spontaneous dielectric anomaly at T_(N) is regarded as arising from the shifts in optical phonon frequencies,and the magnetoelectric coupling is used to interpret the magnetic field induced MD effect.Moreover,an H-T phase diagram is constructed for Ho_(2)Cu_(2)O_(5) and Yb_(2)Cu_(2)O_(5) based on the results of isothermal magnetic and dielectric hysteresis loops.
基金Project supported by the National Basic Research Program of China (Grant No. 2007CB925003)the National Natural Science Foundation of China (Grant No. 50872148)
文摘Different magnetodielectric effects were observed in Bi1-xGdxFeOa ceramics depending on gadolinium content. A positive one was observed in the samples with x ≤ 0.10 at 295 K and 16 K, and a negative one in the sample with x = 0.4 at 16 K. Structure analysis by x-ray diffraction （XRD） reveals that the samples crystallize in the R3c structure （ferroelectrics） for x 〈 0.08 and in the Pbnm structure （paraelectrics） for x ≥ 0.3 at room temperature. Temperaturedependent dielectric response and x-ray diffraction confirm the occurrence of a structural transition in the Pbnm phase at low temperature for the samples with x ≤0.4. While the positive magnetodielectric effects can be attributed to a coupling of magnetic and crystallographic structures of the R3c phase, the observed negative magnetodielectric effect in the Pbnm phase can be associated with a low-temperature modification of the Pbnm structure. The observed dualsigned magnetodielectric effects suggest that the Bi1-xGdxFeO3 oxides are a good prototype for understanding the magnetodielectric coupling mechanism in this kind of materials.
基金support(Basic Scientific Research Start-Up Project Grant No.F.30-401/2017(BSR))to carry out this research work.
文摘Lead-free multiferroic composites of 1−x(K_(0.5)Na_(0.5)NbO_(3−x))(Co_(0.6)Zn_(0.4))(Fe_(1.7)Mn_(0.3))O_(4)(KNN-CZFMO),where x=0.0,0.1,0.2,0.3,0.4,0.5 and 1.0,have been investigated for their structural,morphological,electrical,magnetic,dielectric and magneto-dielectric properties.Presence of KNN and CZFMO crystal structure in each composite has been confirmed from X-ray diffrac-tion analysis(XRD).Cuboidal-shaped grains of KNN and spherical-shaped grains of CZFMO have been observed by scanning electron microscopy(SEM).The room temperature ferroelectric behavior as confirmed by polarization versus electric field(P-E)hysteresis loops has been found to be decreasing with increasing CZFMO concentration.Increasing magnetic ordering with the increase in CZFMO concentration in the prepared composites has been observed by magnetization versus magnetic field(M-H)hysteresis loops.The electrical conductivity of composites has been studied using Jonscher’s universal power law.The room temperature dielectric constant(ε′)and dielectric loss(tanδ)have been observed to decrease with the increase in the frequency of the applied external electric field.The dielectric relaxation behavior has been observed using curve fitting analysis via the Havriliak-Negami relaxation model.Maximum value of the magnetodielectric(MD)effect~−11%at a frequency of 1 kHz with the applied magnetic field of 1 T has been achieved for 0.9 KNN−0.1 CZFMO(x=0.1)composite in the present research work.
