{'fraction_non_alphanumeric': 0.028696194635059263, 'fraction_numerical': 0.017467248908296942, 'mean_word_length': 5.052830188679246, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
High Resolution S/Transmission Electron Microscopy Investigation of Ca3Mn2O7 Phase Transformation under In-situ Heating Condition

The Ca 3 Mn 2 O 7 was proposed to be a prototypical material for achieving the strong magnetoelectric coupling at room temperature. The magnetoelectric coupling in this system can be obtained via the mechanism called “hybrid improper ferroelectricity”. This mechanism includes combining two non-polar mode, i.e. the X 3 tilting mode and the X 2 rotation mode [1]. The combination of the two modes induces ferroelectricity in the material and can potentially couple the ferroelectricity and the ferromagnetism with the same set of modes [2]. The magnetoelectric coupling induced by the hybrid improper ferroelectrics has drawn a lot of interests due to its potential application in the next generation memory devices [3]. The switching via the hybrid improper ferroelectricity mechanism has been demonstrated in several other crystals systems [4], [5]. However, Ca 3 Mn 2 O 7 has shown difficulties with the polarization switching, due to complex domain morphology in the crystal and the polar-nonpolar phase coexistence at room temperature [2]. The high-temperature phase of the Ca 3 Mn 2 O 7 belongs to the I4/mmm space group, and transforms into the low-temperature polar phase of space group A2 1 am via an intermediate non-polar phase of the space group Acaa [6]. The phase transition introduces the oxygen octahedra rotation/tilt degeneracy [7]. The previous DF-TEM study indicates that such degeneracy caused the ferroelectric domains with polarization towards [100]