With substitution of La by Tb in (La_(1-x)Tb_x)_(0.67)Sr_(0.33)MnO_3, the room temperature magnetoresistance △R/R_0drops at first, then undergoes an increase near x≈0.1, and finally drops again. The value of room te...With substitution of La by Tb in (La_(1-x)Tb_x)_(0.67)Sr_(0.33)MnO_3, the room temperature magnetoresistance △R/R_0drops at first, then undergoes an increase near x≈0.1, and finally drops again. The value of room temperaturemagnetoresistance at a field H=12 kOe for (La_(0.9)Tb_(0.1))_(0.67)Sr_(0.33)MnO_3 is -3.56%. The enhancement of the roomtemperature magnetoresistance induced by an appropriate Tb substitution in (La_(1-x)Tb_x)_(0.67)Sr_(0.33)MnO_3 is correlatedwith the shifts of the Curie temperature and metal-insulator temperature to near room temperature. The drop ofthe room temperature magnetoresistance at large Tb doping-contents may be due to its lower T_C and T_(MI) far fromthe room temperature.展开更多
Gd_(0.67)Ca_(0.33)MnO_3(GCMO)thin films grown by laser ablation on SrTiO_3(100)(STO)substrates was studied. Films are highly crystallized, very well epitaxial and single-phased. The ordering magnetic temperature(T_c)o...Gd_(0.67)Ca_(0.33)MnO_3(GCMO)thin films grown by laser ablation on SrTiO_3(100)(STO)substrates was studied. Films are highly crystallized, very well epitaxial and single-phased. The ordering magnetic temperature(T_c)of the films is much higher than the value of bulk samples of similar composition. It is found that the GCMO film exhibits a reversal of its magnetization at low temperature when cooled under a magnetic field. The negative magnetization is a consequence of the rapid increase(～1/T)with decreasing temperature of the magnetization of a sublattice aligned antiparallel to the local field, relative to the magnetic contribution of a second sublattice which is aligned parallel to the applied field.展开更多
LaSrMnOfilms are deposited on(001) silicon substrates,in which the silicon surfaces have artificially been treated into the scallops-like,pyramid-like,and smooth polishing structure,by pulsed laser deposition.The magn...LaSrMnOfilms are deposited on(001) silicon substrates,in which the silicon surfaces have artificially been treated into the scallops-like,pyramid-like,and smooth polishing structure,by pulsed laser deposition.The magnetoresistances of the films on etched substrates under low applied field are very sensitive to the applied field,and much larger(14.3% for acid-etched,and 42.9% for alkali-etched) than that on the polished Si at 5 K.Zero-field-cooled and field-cooled magnetization behaviors are measured and analyzed.Remarkable upturn behaviors in temperature-dependent resistivity for all samples are observed at low temperature,which follows the Efros-Shkloskii variable range hopping law and the Arrhenius law.We believe that the rough surface may be useful in device design.展开更多
Structure model of charge-ordered La_0.33 Ca_0.67 MnO_3, perovskite is one of current focused study in condensed matter physics. There are great discrepancies in previous studies in this field. Our transmission electr...Structure model of charge-ordered La_0.33 Ca_0.67 MnO_3, perovskite is one of current focused study in condensed matter physics. There are great discrepancies in previous studies in this field. Our transmission electron microscopy study confirms Wigner crystal model with transverse displacement and is not consisent with the hi-stripe model with longitudinal displacement. We observed incommensurate modulation and anti-phase domains with a displacement vector a_co/3 in charge--ordered La_0.33 Ca_0.67 MnO_3, perovskite.展开更多
The effects of Al ion doping on the Mn site were studied for the colossal magnetoresistance material La_(0.67)Ca_(0.33)MnO_3. It is found that the volume of the crystal cell decreases monotonically when the population...The effects of Al ion doping on the Mn site were studied for the colossal magnetoresistance material La_(0.67)Ca_(0.33)MnO_3. It is found that the volume of the crystal cell decreases monotonically when the population of Al^(3+) increases across the entire doping range. As the Al^(3+) population increases, the resistance of the material rises rapidly, while the insulator-metal transition temperature T_(IM) decreases linearly. At small Al^(3+) dosage, a thermal activation model properly describes the transport properties at T>T_(IM), while a metallic model is more suitable at T<T_(IM). The variation of transport properties with the change of Al dosage may be attributed to lattice distortion caused by the destruction of Mn^(3+)-O^(2-)-Mn^(4+) double exchange channel as a result of Al^(3+)-doping. The doped Al^(3+) ions may modify the local field for electrons so to affect the transport properties.展开更多
The La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3+δ</sub>/Pr<sub>0.7</sub>Ca<sub>0.3</sub>MnO<sub>3+δ</sub>/La<sub>0.67</sub>Sr<su...The La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3+δ</sub>/Pr<sub>0.7</sub>Ca<sub>0.3</sub>MnO<sub>3+δ</sub>/La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3+δ</sub>（LPL） trilayered films on （100） LaAlO<sub>3</sub> substrates are prepared by using direct current （DC） magnetron sputtering method. The results obtained by means of X-ray powder diffractometer show that all films are the high quality epitaxial films. The results gained by SQUID magnetometer indicate that there is a magnetic coupling in the LPL trilayered films. The resistivities of LSMO, PCMO and LPL films are measured using standard four-probe method and analyzed logρ-1/T curve. From the results it is concluded that the middle-layered PCMO which is ferromagnetic may play a role of intra-magnetic field, which weakens the paramagnetism of LSMO film, lowers ρ<sub>max</sub> and enlarges T<sub>p</sub> which is the transition temperature from metal to insulator, just as the applied magnetic field does. And the middle-layered PCMO may induce the change of the density of states in the LSMO’s gap. The two reasons above make the resistivity and T<sub>p</sub>展开更多
THE colossal magnetoresistance (CMR) effects in doped perovskite-like oxide have stimulatedconsiderable attention to the study of fundamental physics and the application of new type ma-terials. It was reported that a ...THE colossal magnetoresistance (CMR) effects in doped perovskite-like oxide have stimulatedconsiderable attention to the study of fundamental physics and the application of new type ma-terials. It was reported that a large CMR effect and a high critical temperature T_c shown展开更多
We report the preparation of epitaxial La_(0.7)Sr_(0.3)MnO_(3) thin films grown on(001)-oriented 0.72Pb(Mg_(1/3)Nb_(2/3))TO_(3)-0.28PbTiO_(3) substrates by the sol–gel technique.The phase structure,magnetic propertie...We report the preparation of epitaxial La_(0.7)Sr_(0.3)MnO_(3) thin films grown on(001)-oriented 0.72Pb(Mg_(1/3)Nb_(2/3))TO_(3)-0.28PbTiO_(3) substrates by the sol–gel technique.The phase structure,magnetic properties and magnetoresistance of the samples are investigated by using high solution X-ray diffraction,atomic force microscopy,physical property measurement system,respectively.The La_(0.7)Sr_(0.3)MnO_(3) thin films display a well-defined hysteresis loop and typical ferromagnetism behavior at lower temperature.High magnetoresistance at 5 T of 42%appears at 227K for La_(0.7)Sr_(0.3)MnO_(3) thin film.展开更多
文摘With substitution of La by Tb in (La_(1-x)Tb_x)_(0.67)Sr_(0.33)MnO_3, the room temperature magnetoresistance △R/R_0drops at first, then undergoes an increase near x≈0.1, and finally drops again. The value of room temperaturemagnetoresistance at a field H=12 kOe for (La_(0.9)Tb_(0.1))_(0.67)Sr_(0.33)MnO_3 is -3.56%. The enhancement of the roomtemperature magnetoresistance induced by an appropriate Tb substitution in (La_(1-x)Tb_x)_(0.67)Sr_(0.33)MnO_3 is correlatedwith the shifts of the Curie temperature and metal-insulator temperature to near room temperature. The drop ofthe room temperature magnetoresistance at large Tb doping-contents may be due to its lower T_C and T_(MI) far fromthe room temperature.
文摘Gd_(0.67)Ca_(0.33)MnO_3(GCMO)thin films grown by laser ablation on SrTiO_3(100)(STO)substrates was studied. Films are highly crystallized, very well epitaxial and single-phased. The ordering magnetic temperature(T_c)of the films is much higher than the value of bulk samples of similar composition. It is found that the GCMO film exhibits a reversal of its magnetization at low temperature when cooled under a magnetic field. The negative magnetization is a consequence of the rapid increase(～1/T)with decreasing temperature of the magnetization of a sublattice aligned antiparallel to the local field, relative to the magnetic contribution of a second sublattice which is aligned parallel to the applied field.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1332205,11274153,11204124,and 51202108)
文摘LaSrMnOfilms are deposited on(001) silicon substrates,in which the silicon surfaces have artificially been treated into the scallops-like,pyramid-like,and smooth polishing structure,by pulsed laser deposition.The magnetoresistances of the films on etched substrates under low applied field are very sensitive to the applied field,and much larger(14.3% for acid-etched,and 42.9% for alkali-etched) than that on the polished Si at 5 K.Zero-field-cooled and field-cooled magnetization behaviors are measured and analyzed.Remarkable upturn behaviors in temperature-dependent resistivity for all samples are observed at low temperature,which follows the Efros-Shkloskii variable range hopping law and the Arrhenius law.We believe that the rough surface may be useful in device design.
文摘Structure model of charge-ordered La_0.33 Ca_0.67 MnO_3, perovskite is one of current focused study in condensed matter physics. There are great discrepancies in previous studies in this field. Our transmission electron microscopy study confirms Wigner crystal model with transverse displacement and is not consisent with the hi-stripe model with longitudinal displacement. We observed incommensurate modulation and anti-phase domains with a displacement vector a_co/3 in charge--ordered La_0.33 Ca_0.67 MnO_3, perovskite.
基金supported by Beijing Natural Science Foundation(Z190010)the National Key Basic Research Program of China(2017YFA0303604,2019YFA0308500)+4 种基金the Key research projects of Frontier Science of Chinese Academy of Sciences(QYZDB-SSW-JSC035)the Youth Innovation Promotion Association of CAS(2018008)the National Natural Science Foundation of China(51672307,51991344,52025025,52072400,12074416,12074434,52250402)China National Postdoctoral Program for Innovative Talents(BX20220166)China Postdoctoral Science Foundation(2023M731863)。
文摘The effects of Al ion doping on the Mn site were studied for the colossal magnetoresistance material La_(0.67)Ca_(0.33)MnO_3. It is found that the volume of the crystal cell decreases monotonically when the population of Al^(3+) increases across the entire doping range. As the Al^(3+) population increases, the resistance of the material rises rapidly, while the insulator-metal transition temperature T_(IM) decreases linearly. At small Al^(3+) dosage, a thermal activation model properly describes the transport properties at T>T_(IM), while a metallic model is more suitable at T<T_(IM). The variation of transport properties with the change of Al dosage may be attributed to lattice distortion caused by the destruction of Mn^(3+)-O^(2-)-Mn^(4+) double exchange channel as a result of Al^(3+)-doping. The doped Al^(3+) ions may modify the local field for electrons so to affect the transport properties.
基金Project supported by the Chinese Academy of Sciences the Foundation of State ScienceTechnology Commission of China
文摘The La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3+δ</sub>/Pr<sub>0.7</sub>Ca<sub>0.3</sub>MnO<sub>3+δ</sub>/La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3+δ</sub>（LPL） trilayered films on （100） LaAlO<sub>3</sub> substrates are prepared by using direct current （DC） magnetron sputtering method. The results obtained by means of X-ray powder diffractometer show that all films are the high quality epitaxial films. The results gained by SQUID magnetometer indicate that there is a magnetic coupling in the LPL trilayered films. The resistivities of LSMO, PCMO and LPL films are measured using standard four-probe method and analyzed logρ-1/T curve. From the results it is concluded that the middle-layered PCMO which is ferromagnetic may play a role of intra-magnetic field, which weakens the paramagnetism of LSMO film, lowers ρ<sub>max</sub> and enlarges T<sub>p</sub> which is the transition temperature from metal to insulator, just as the applied magnetic field does. And the middle-layered PCMO may induce the change of the density of states in the LSMO’s gap. The two reasons above make the resistivity and T<sub>p</sub>
文摘THE colossal magnetoresistance (CMR) effects in doped perovskite-like oxide have stimulatedconsiderable attention to the study of fundamental physics and the application of new type ma-terials. It was reported that a large CMR effect and a high critical temperature T_c shown
基金financially supported by International Science&Technology Cooperation Program of China(Grant no.2011DFA51880)111 Project of China(B14040).
文摘We report the preparation of epitaxial La_(0.7)Sr_(0.3)MnO_(3) thin films grown on(001)-oriented 0.72Pb(Mg_(1/3)Nb_(2/3))TO_(3)-0.28PbTiO_(3) substrates by the sol–gel technique.The phase structure,magnetic properties and magnetoresistance of the samples are investigated by using high solution X-ray diffraction,atomic force microscopy,physical property measurement system,respectively.The La_(0.7)Sr_(0.3)MnO_(3) thin films display a well-defined hysteresis loop and typical ferromagnetism behavior at lower temperature.High magnetoresistance at 5 T of 42%appears at 227K for La_(0.7)Sr_(0.3)MnO_(3) thin film.
