Titanates with the perovskite structure, including ferroelectrics （e.g., BaTiO3） and ferromagnetic ones （e.g., YTiO3）, are important functional materials. Recent theoretical studies predicted multi- ferroic states...Titanates with the perovskite structure, including ferroelectrics （e.g., BaTiO3） and ferromagnetic ones （e.g., YTiO3）, are important functional materials. Recent theoretical studies predicted multi- ferroic states in strained EuTiO3 and titanate superlattices, the former of which has already been experimental confirmed. Here, a first-principles calculation is performed to investigate the struc- tural, magnetic, and electronic properties of Y half-substituted LaTiO3. Our results reveal that the magnetism of Yo.sLao.5TiO3 sensitively depends on its structural details because of the inher- ent phase competition. The lowest energy state is the ferromagnetic state, resulting in 0.25 μB/Ti. Furthermore, some configurations of Y0.500La0.5TiO3 exhibit hybrid improper polarizations, which can be significantly affected by magnetism, resulting in the multiferroic properties. Because of the quenching disorder of substitution, the real Y0.5La0.5TiO3 material with random A-site ions may exhibit interesting relaxor behaviors.展开更多
Ferroelectric and magnetic properties of Fe1-xMnxV2O4 （0 ≤ x ≤ 0.5） spinels are investigated on the basis of dielectric, polarization, and susceptibility measurements. Ferroeleetric polarization is discovered in c...Ferroelectric and magnetic properties of Fe1-xMnxV2O4 （0 ≤ x ≤ 0.5） spinels are investigated on the basis of dielectric, polarization, and susceptibility measurements. Ferroeleetric polarization is discovered in collinear ferrimagnetic and Yafet-Kittel magnetic phases for 0.1 ≤ x ≤ 0.4, which can be tuned by a magnetic field. As orbital-active FJ＋ is substituted with Mn2＋, ferroeleetric polarization decreases for 0 ≤ x ≤ 0.4 and disappears for x=0.5. We propose that the two polar components in ferroelectric polarization originate from the exchange striction mechanism and the spin-current model, respectively.展开更多
We have investigated the low-temperature magnetism and spin-lattice coupling in （Bio.46Nao.46Bao.os）TiO3 ：Co in order to understand the magnetoelectric effect in such artificially synthesized dilute magnetic ferroe...We have investigated the low-temperature magnetism and spin-lattice coupling in （Bio.46Nao.46Bao.os）TiO3 ：Co in order to understand the magnetoelectric effect in such artificially synthesized dilute magnetic ferroelectrics. It is revealed that the as-prepared （Bio.46Nao.46Bao.os）TiO3：Co at Co content of 20%~30% exhibits fascinating ferrimagnetism which is robust against magnetic field, the abnormal spin lattice coupling characterized by a negative magnetostriction effect; and the suppressed magnetic moment within the temperature range of 30 K-50 K is identified. These magnetic behaviours at low temperatures can be explained by the competition between the ferrimagnetic response and the magnetic moment suppression induced by the abnormal spin lattice coupling effect. Finally, the ferroelectric and magnetodielectric properties are also discussed.展开更多
This article aims to investigate the possibility to turn the multiferroic orders and magnetocapacitance effect close to/above room temperature in nanosized GaFeO3 ceramics by a sol-gel preparation method and substitut...This article aims to investigate the possibility to turn the multiferroic orders and magnetocapacitance effect close to/above room temperature in nanosized GaFeO3 ceramics by a sol-gel preparation method and substitution with non-magnetic Zn atoms. Therefore, in this work, we have synthesized a series of nanocrystalline Ga1-xZnxFeO3(GZFO, x = 0, 0.01, 0.05 and 0.1) ceramic samples and study the effect of Zn substitution on their structural, magnetic, and electric properties. All the GZFO samples have an orthorhombic structure with Pc21n space group and the value of lattice parameters increase systematically with increasing Zn concentration. Interestingly, it shows that magnetic and electric properties are strongly dependent on the Zn substitution concentration. Based on the results of temperature-dependent magnetizations, M(T), it is observed that with increasing Zn-content up to 0.10, the ferrimagnetic transition temperature (TC) increases from 306 to 320 K. It is also found that the nanocrystalline Zn-doped GaFeO3 (GFO) samples exhibit the characteristics of ferroelectricity at room temperature. Furthermore, the?magnetization, ferroelectric polarization and magnetocapacitance of Zn-doped GFO nanosized ceramics are enhanced compared to those of the pristine sample of GFO ferrite. These results open wide perspectives for the applications of room temperature multiferroic devices.展开更多
We report the magnetoelectric (ME) coupling in ME composites composed of NiFe<sub>2</sub>O<sub>4</sub> (NFO) or metglas as magnetostrictive phases and BaTiO<sub>3</sub> (BTO) as pie...We report the magnetoelectric (ME) coupling in ME composites composed of NiFe<sub>2</sub>O<sub>4</sub> (NFO) or metglas as magnetostrictive phases and BaTiO<sub>3</sub> (BTO) as piezoelectric phase, targeting lead free magetnic field sensors. NFO and BTO phases were synthesized by solid state sintering method and further characterized by using XRD and FESEM techniques. The P-E hysteresis curve shows good ferroelectric behavior with saturation polarization of P<sub>s</sub> = 15.87 C/cm<sup>2</sup> and coercive electric field of 130 kV/cm. The ME response was characterized as a function of dc magnetic field at a fixed frequency. The transverse ME voltage coefficient, αME31 shows 2 times larger magnitude than that of longitudinal ME voltage coefficient, α<sub>ME31</sub>. The maximum α<sub>ME31</sub> of 37 mV/cm•Oe (@H<sub>dc</sub> = 250 Oe) is observed for NFO/BTO/NFO ME composites with thickness ratio of t<sub>m</sub>/t<sub>p</sub> = 1.0. The ME coupling is further enhanced by replacing NFO layers by highly magnetostrictive metglas layers. Metglas/BTO/metglas laminates show large α<sub>ME31</sub> value of 81 mV/cm•Oe at relatively lower H<sub>dc</sub> of 145 Oe. The present laminates can offer promising opportunities of engineering environmental friendly ME laminate for applications in ME devices such as energy harvester and magnetic field sensors.展开更多
A magnonic counterpart to optical frequency combs is vital for high-precision magnonic frequency metrology and spectroscopy.Here,we present an efficient mechanism for the generation of robust magnonic frequency combs ...A magnonic counterpart to optical frequency combs is vital for high-precision magnonic frequency metrology and spectroscopy.Here,we present an efficient mechanism for the generation of robust magnonic frequency combs in a yttrium iron garnet(YIG)sphere via magnetostrictive effects.We show that magnonic and vibrational dynamics in the ferrimagnetic sphere can be substantively modified in the presence of magnetostrictive effects,which results in degenerate and non-degenerate magnonic four-wave mixing and frequency conversion.Particularly,resonantly enhanced magnetostrictive effects can induce phonon laser action above a threshold,which leads to significant magnonic nonlinearity and enables a potentially practical scheme for the generation of robust magnonic frequency combs.Numerical calculations of both magnonic and phononic dynamics show excellent agreement with this theory.These results deepen our understanding of magnetostrictive interaction,open a novel and efficient pathway to realize magnonic frequency conversion and mixing in a magnonic device,and provide a sensitive tool for precision measurement.展开更多
Ferrimagnets, which contain the advantages of both ferromagnets(detectable moments) and antiferromagnets(ultrafast spin dynamics), have recently attracted great attention. Here, we report the optimization of epitaxial...Ferrimagnets, which contain the advantages of both ferromagnets(detectable moments) and antiferromagnets(ultrafast spin dynamics), have recently attracted great attention. Here, we report the optimization of epitaxial growth of a tetragonal perpendicularly magnetized ferrimagnet Mn_(2)Ga on MgO. Electrical transport, magnetic properties and the anomalous Hall effect(AHE) were systematically studied. Furthermore, we successfully integrated high-quality epitaxial ferrimagnetic Mn_(2)Ga thin films onto ferroelectric 0.7PbMg_(1/3)Nb_(2/3)O_(3)–0.3PbTiO_(3) single crystals with a MgO buffer layer. It was found that the AHE of such a ferrimagnet can be effectively modulated by a small electric field over a large temperature range in a nonvolatile manner. This work thus demonstrates the great potential of ferrimagnets for developing high-density and low-power spintronic devices.展开更多
文摘Titanates with the perovskite structure, including ferroelectrics （e.g., BaTiO3） and ferromagnetic ones （e.g., YTiO3）, are important functional materials. Recent theoretical studies predicted multi- ferroic states in strained EuTiO3 and titanate superlattices, the former of which has already been experimental confirmed. Here, a first-principles calculation is performed to investigate the struc- tural, magnetic, and electronic properties of Y half-substituted LaTiO3. Our results reveal that the magnetism of Yo.sLao.5TiO3 sensitively depends on its structural details because of the inher- ent phase competition. The lowest energy state is the ferromagnetic state, resulting in 0.25 μB/Ti. Furthermore, some configurations of Y0.500La0.5TiO3 exhibit hybrid improper polarizations, which can be significantly affected by magnetism, resulting in the multiferroic properties. Because of the quenching disorder of substitution, the real Y0.5La0.5TiO3 material with random A-site ions may exhibit interesting relaxor behaviors.
基金Supported by the National Basic Research Program of China under Grant Nos 2011CB921904 and 2012CB927402the National Natural Science Foundation of China under Grant Nos 11074142 and 11021464+1 种基金the Key Project of the Ministry of Education of China under Grant No 309003the Tsinghua TNList Cross-discipline Foundation
文摘Ferroelectric and magnetic properties of Fe1-xMnxV2O4 （0 ≤ x ≤ 0.5） spinels are investigated on the basis of dielectric, polarization, and susceptibility measurements. Ferroeleetric polarization is discovered in collinear ferrimagnetic and Yafet-Kittel magnetic phases for 0.1 ≤ x ≤ 0.4, which can be tuned by a magnetic field. As orbital-active FJ＋ is substituted with Mn2＋, ferroeleetric polarization decreases for 0 ≤ x ≤ 0.4 and disappears for x=0.5. We propose that the two polar components in ferroelectric polarization originate from the exchange striction mechanism and the spin-current model, respectively.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50832002 and 10874075)the National Basic Research Program of China (Grant Nos. 2009CB613303 and 2009CB929501)the Natural Science Foundation of Jiangsu Province,China (Grant No. BK2008024)
文摘We have investigated the low-temperature magnetism and spin-lattice coupling in （Bio.46Nao.46Bao.os）TiO3 ：Co in order to understand the magnetoelectric effect in such artificially synthesized dilute magnetic ferroelectrics. It is revealed that the as-prepared （Bio.46Nao.46Bao.os）TiO3：Co at Co content of 20%~30% exhibits fascinating ferrimagnetism which is robust against magnetic field, the abnormal spin lattice coupling characterized by a negative magnetostriction effect; and the suppressed magnetic moment within the temperature range of 30 K-50 K is identified. These magnetic behaviours at low temperatures can be explained by the competition between the ferrimagnetic response and the magnetic moment suppression induced by the abnormal spin lattice coupling effect. Finally, the ferroelectric and magnetodielectric properties are also discussed.
文摘This article aims to investigate the possibility to turn the multiferroic orders and magnetocapacitance effect close to/above room temperature in nanosized GaFeO3 ceramics by a sol-gel preparation method and substitution with non-magnetic Zn atoms. Therefore, in this work, we have synthesized a series of nanocrystalline Ga1-xZnxFeO3(GZFO, x = 0, 0.01, 0.05 and 0.1) ceramic samples and study the effect of Zn substitution on their structural, magnetic, and electric properties. All the GZFO samples have an orthorhombic structure with Pc21n space group and the value of lattice parameters increase systematically with increasing Zn concentration. Interestingly, it shows that magnetic and electric properties are strongly dependent on the Zn substitution concentration. Based on the results of temperature-dependent magnetizations, M(T), it is observed that with increasing Zn-content up to 0.10, the ferrimagnetic transition temperature (TC) increases from 306 to 320 K. It is also found that the nanocrystalline Zn-doped GaFeO3 (GFO) samples exhibit the characteristics of ferroelectricity at room temperature. Furthermore, the?magnetization, ferroelectric polarization and magnetocapacitance of Zn-doped GFO nanosized ceramics are enhanced compared to those of the pristine sample of GFO ferrite. These results open wide perspectives for the applications of room temperature multiferroic devices.
文摘We report the magnetoelectric (ME) coupling in ME composites composed of NiFe<sub>2</sub>O<sub>4</sub> (NFO) or metglas as magnetostrictive phases and BaTiO<sub>3</sub> (BTO) as piezoelectric phase, targeting lead free magetnic field sensors. NFO and BTO phases were synthesized by solid state sintering method and further characterized by using XRD and FESEM techniques. The P-E hysteresis curve shows good ferroelectric behavior with saturation polarization of P<sub>s</sub> = 15.87 C/cm<sup>2</sup> and coercive electric field of 130 kV/cm. The ME response was characterized as a function of dc magnetic field at a fixed frequency. The transverse ME voltage coefficient, αME31 shows 2 times larger magnitude than that of longitudinal ME voltage coefficient, α<sub>ME31</sub>. The maximum α<sub>ME31</sub> of 37 mV/cm•Oe (@H<sub>dc</sub> = 250 Oe) is observed for NFO/BTO/NFO ME composites with thickness ratio of t<sub>m</sub>/t<sub>p</sub> = 1.0. The ME coupling is further enhanced by replacing NFO layers by highly magnetostrictive metglas layers. Metglas/BTO/metglas laminates show large α<sub>ME31</sub> value of 81 mV/cm•Oe at relatively lower H<sub>dc</sub> of 145 Oe. The present laminates can offer promising opportunities of engineering environmental friendly ME laminate for applications in ME devices such as energy harvester and magnetic field sensors.
文摘A magnonic counterpart to optical frequency combs is vital for high-precision magnonic frequency metrology and spectroscopy.Here,we present an efficient mechanism for the generation of robust magnonic frequency combs in a yttrium iron garnet(YIG)sphere via magnetostrictive effects.We show that magnonic and vibrational dynamics in the ferrimagnetic sphere can be substantively modified in the presence of magnetostrictive effects,which results in degenerate and non-degenerate magnonic four-wave mixing and frequency conversion.Particularly,resonantly enhanced magnetostrictive effects can induce phonon laser action above a threshold,which leads to significant magnonic nonlinearity and enables a potentially practical scheme for the generation of robust magnonic frequency combs.Numerical calculations of both magnonic and phononic dynamics show excellent agreement with this theory.These results deepen our understanding of magnetostrictive interaction,open a novel and efficient pathway to realize magnonic frequency conversion and mixing in a magnonic device,and provide a sensitive tool for precision measurement.
基金the National Natural Science Foundation of China(Nos.52121001,51822101,51861135104 and 51771009)。
文摘Ferrimagnets, which contain the advantages of both ferromagnets(detectable moments) and antiferromagnets(ultrafast spin dynamics), have recently attracted great attention. Here, we report the optimization of epitaxial growth of a tetragonal perpendicularly magnetized ferrimagnet Mn_(2)Ga on MgO. Electrical transport, magnetic properties and the anomalous Hall effect(AHE) were systematically studied. Furthermore, we successfully integrated high-quality epitaxial ferrimagnetic Mn_(2)Ga thin films onto ferroelectric 0.7PbMg_(1/3)Nb_(2/3)O_(3)–0.3PbTiO_(3) single crystals with a MgO buffer layer. It was found that the AHE of such a ferrimagnet can be effectively modulated by a small electric field over a large temperature range in a nonvolatile manner. This work thus demonstrates the great potential of ferrimagnets for developing high-density and low-power spintronic devices.
