Ultrasonic study on charge ordering, magnetic, and structural changes in La0.25Ca0.75Mn0.93Cr0.07O3

Abstract

The longitudinal and transverse ultrasonic velocities and attenuations, the transport and magnetic properties, as well as the structural changes of polycrystalline La0.25Ca0.75Mn0.93Cr0.07O3 have been studied systematically. A velocity minimum and an attenuation peak for both longitudinal and transverse waves occur around the temperature Tco of charge ordering transition accompanied by the structural change from a cubic to a tetragonal phase. Near temperature TN (where the c-axis length shows a maximum), the sharp decrease of velocities for both waves and the appearance of a longitudinal attenuation peak are attributed to the antiferromagnetic transition together with the anomalous change in c-axis length of the tetragonal phase. The simultaneous occurrence of the ultrasonic, lattice, charge ordering, magnetic, and transport anomalous characteristics indicates the strong electron–phonon and spin–phonon interactions in the system.

Charge ordering correlated ultrasonic anomalies in La1/3Sr2/3Fe1−xCrxO3 perovskites

“…While in La 1/3 Sr 2/3 Fe 1−x Cr x O 3 , the V l /V lmin around T CO is larger than 3% in all samples, which cannot be explained only based on spin-phonon coupling near a conventional AFM phase transition. In fact, the similar phenomenon has been well discussed in chargeordered manganites on both experimental and theoretical levels [6,12], which is interpreted by the electron-phonon coupling originated from the Jahn-Teller effect of Mn 3+ . Since Fe 4+ is isoelectronic with Mn 3+ , it is reasonable to attribute this ultrasonic anomaly in La 1/3 Sr 2/3 Fe 1−x Cr x O 3 to the similar electron-phonon coupling via the Jahn-Teller effect of Fe 4+ .…”

“…It is well known that in many CO and CD systems, the charges strongly couple with the lattice. For example, the electron-phonon coupling, which is caused by the Jahn-Teller distortion of Mn 3+ , plays an important role for the CO state in manganites [6]. And in YNiO 3 and CaFeO 3 , the breathing-type lattice distortion has been found with the CD transition [7,8].…”

“…Ultrasonic responses to the formation of the CO state in manganites have been theoretically and experimentally studied [6,12]. Recently, this technique has been used to study the CO transition in La 1/3 Sr 2/3 FeO 3 and anomalies in sound velocity have been observed, which indicates that the sound velocity measurement is a very useful tool to monitor the lattice distortions in this system [13].…”

Low Frequency Internal Friction Study of Phase Transition in La0.95K0.05MnO3 Bulk Materials

“…There exist already several reports on the internal friction and elastic modulus measurements in colossal magnetoresistance materials [12][13][14][15]. A dramatic change in the elastic modulus and a peak in the internal friction are observed and are associated with the PM-FM phase transition.…”

Short-range charge-ordering correlated elastic anomalies in La2/3Sr1/3FeO3

“…1, it can be seen that the relative increase is about 2.5% for longitudinal ultrasonic velocity. While in representative sample of charge ordered manganites, such as La 0.25 Ca 0.75 Mn 0.93 Cr 0.07 O 3 , this value is more that 20% [17]. So the resulting lattice distortion in La 0.25 Ca 0.75 Mn 0.93 Cr 0.07 O 3 can be detected by the XRD measurement, while the Jahn-Teller effect of Fe 4 þ is too weak to be detected by neutron diffraction.…”