Learning Dialogues orchestrated with BookRoll: Effects on Engagement and Learning in an Undergraduate Physics course

With COVID-19 pandemic forcing academic institutions to shift to emergency remote teaching (ERT), teachers worldwide are attempting several strategies to engage their learners. Even though existing research in online learning suggests that effectiveness of the online session is more dependent on pedagogical design rather than technology feature, teachers may still focus on the intricacies of the technology. In this paper, we present the evolution of an active learning pedagogy, supported by technology (eBook reader—BookRoll, Analytics Dashboard—LAViEW), for an undergraduate physics classroom across a semester that was affected by the lockdown due to pandemic. The technology-enhanced pedagogy evolved in three phases—technology used in “Content Focus” mode, technology used in “Problem Focus” mode and technology used in “Learning Dialogue Focus” mode. The entire activities were designed and implemented within the technology-enhanced and evidence-based education and learning (TEEL) ecosystem, which supported integration of learning technologies with analytics system. Comparison of the student’s learning logs indicated that there was a sustained engagement in the learning activities conducted during the blended (before lockdown) and online mode (during lockdown). We had conducted one-way ANOVA to compare the post-test scores for each teaching phase and found statistically significant differences in the latter phases. A preliminary qualitative analysis of the learner artifacts generated as memos in BookRoll during each phase revealed that students were posing conceptual clarifications during the latter phases. These were also having greater alignment with the session agenda and showed construction of new knowledge based on the seed knowledge provided during the instructor–learner interaction sessions. The study provides key insights into how reflection and practice by both learner and teacher improves the acceptance of technology-enabled pedagogy

Gallium Substituted "114" YBaFe4O7: From a ferrimagnetic cluster glass to a cationic disordered spin glass

The study of the ferrites YBaFe4-xGaxO7 shows that the substitution of Ga for Fe in YBaFe4O7 stabilizes the hexagonal symmetry for 0.40 < x < 0.70, at the expense of the cubic one. Using combined measurements of a. c. and d. c. magnetization, we establish that Ga substitution for Fe in YBaFe4O7 leads to an evolution from a geometrically frustrated spin glass (for x = 0) to a cationic disorder induced spin glass (x = 0.70). We also find an intermediate narrow range of doping where the samples are clearly phase separated having small ferrimagnetic clusters embedded in a spin glass matrix. The origin of the ferrimagnetic clusters lies in the change in symmetry of the samples from cubic to hexagonal (and a consequent lifting of the geometrical frustration) as a result of Ga doping. We also show the presence of exchange bias and domain wall pinning in these samples. The cause of both these effects can be traced back to the inherent phase separation present in the samples.Comment: 25 pages, 10 figure

Flip & Pair – a strategy to augment a blended course with active-learning components: effects on engagement and learning

Blended learning technique has adapted many new digitized tools to facilitate students with flexible and self-phased learning opportunities. The flipped classroom strategy, one of the blended learning models has been limited by low engagement of students in the online component. In the present study, we augment a Flip and Pair (F&P), an active-learning strategy into the blended learning course. Following the AB type single group quasi-experimental design, we evaluated the effects of F&P strategy on the student’s engagement and learning while orchestrating it for an undergraduate engineering physics course. Our results highlighted that there is a positive correlation between the engagement (computed based on learning logs of TEEL (Technology-enhanced and Evidence-based Education and Learning) platform in the F&P activities with that of the performance score (knowledge quizzes and final exam). F&P strategy had a better contribution compared to Flip and Traditional Teaching (F&TT) strategy with respect to both engagement and performance. Also, students exhibited a positive perception of learning and engagement. Based on our findings, we identified the key instructional measures that an instructor can follow to increase student engagement while using the F&P strategy

Geometric and disorder -- type magnetic frustration in ferrimagnetic "114" Ferrites: Role of diamagnetic Li+ and Zn2+ cation substitution

The comparative study of the substitution of zinc and lithium for iron in the "114" ferrites, YBaFe4O7 and CaBaFe4O7, shows that these diamagnetic cations play a major role in tuning the competition between ferrimagnetism and magnetic frustration in these oxides. The substitution of Li or Zn for Fe in the cubic phase YBaFe4O7 leads to a structural transition to a hexagonal phase YBaFe4-xMxO7, for M = Li (0.30 < x < 0.75) and for M = Zn (0.40 < x < 1.50). It is seen that for low doping values i.e. x = 0.30 (for Li) and x = 0.40 (for Zn), these diamagnetic cations induce a strong ferrimagnetic component in the samples, in contrast to the spin glass behaviour of the cubic phase. In all the hexagonal phases, YBaFe4-xMxO7 and CaBaFe4-xMxO7 with M = Li and Zn, it is seen that in the low doping regime (x ~ 0.3 to 0.5), the competition between ferrimagnetism and 2 D magnetic frustration is dominated by the average valency of iron. In contrast, in the high doping regime (x ~ 1.5), the emergence of a spin glass is controlled by the high degree of cationic disorder, irrespective of the iron valency.Comment: 2 tables, 7 figure

Competition between Ferrimagnetism and Magnetic Frustration in Zinc Substituted YBaFe4O7

The substitution of zinc for iron in YBaFe4O7 has allowed the oxide series YBaFe4-xZnxO7, with 0.40 < x < 1.50, belonging to the "114" structural family to be synthesized. These oxides crystallize in the hexagonal symmetry (P63mc), as opposed to the cubic symmetry (F-43m) of YBaFe4O7. Importantly, the d.c. magnetization shows that the zinc substitution induces ferrimagnetism, in contrast to the spin glass behaviour of YBaFe4O7. Moreover, a.c. susceptibility measurements demonstrate that concomitantly these oxides exhibit a spin glass or a cluster glass behaviour, which increases at the expense of ferrimagnetism, as the zinc content is increased. This competition between ferrimagnetism and magnetic frustration is interpreted in terms of lifting of the geometric frustration, inducing the magnetic ordering, and of cationic disordering, which favours the glassy state.Comment: 24 pages, 10 figure

Learning Dialogues orchestrated with BookRoll: A Case Study of Undergraduate Physics Class During COVID-19 Lockdown

28th International Conference on Computers in Education, 23-27 November 2020, Web conference.With COVID-19 pandemic forcing academic institutions to shift to Emergency Remote Teaching strategies, teachers worldwide are attempting several strategies to engage their learners. Even though existing research in online learning has proven that effectiveness of the online session is more dependent on pedagogical design rather than technology features, most teachers still focus on the intricacies of the technology. In this paper we present the adaptation of an active learning pedagogy - Learning Dialogue (LeD), for an undergraduate physics classroom. We used the eBook reader BookRoll to orchestrate an LeD along with the support of a video conferencing tool and a dashboard that provides immediate input on the engagement. The adaptation of the strategy utilized the appropriate affordance of each tool available in generating an engaging session for the students. Comparison of the student artefacts (memos in BookRoll) between regular face-to-face classroom session and online session indicated that there is a sustained engagement in the online class. Preliminary qualitative analysis also shows that the students were posing good conceptual clarifications/questions aligned with the session agend

Calcium zinc manganites, Ca4Mn7Zn3O21−δ(0.5<δ<2.5)Ca_4Mn_7Zn_3O_{21 -\delta} (0.5<\delta <2.5) with beta-alumina or magnetoplumbite-type structure and their nonlinear electrical transport and magnetic properties

Phase-pure calcium zinc manganite, $Ca_4Mn_7Zn_3O_{21 -\delta}$ has been synthesized by the solid-state reaction between $CaMnO_3$, ZnO and $Mn_3O_4$ at $\sim 1300^oC$. Conversion of $Ca_4Mn_7Zn_3O_{21-\delta}$ to $Ca_4Mn_7Zn_3O_{19\pm \delta}$ occurs at 1330–1350°C which is influenced by the oxygen nonstoichiometry associated with increasing $Mn^{3+}/Mn^{4+}$ ratio. The $Ca_4Mn_7Zn_3O_{21-\delta}$ phase is rhombohedral (space group=R3¯m) and has the $\beta"$-alumina (BA)- type structure consisting dominantly of $Mn^{4+} (3d^3)$ ions. The $Ca_4Mn_7Zn_3O_{19 \pm \delta}$ is hexagonal (space group=$P6_3/mmc$) having the magnetoplumbite (MP)-type structure containing dominantly $Mn^{3+} (3d^4)$ ions. The electrical transport properties of $Ca_4Mn_7Zn_3O_{21 -\delta}$ and $Ca_4Mn_7Zn_3O_{19 \pm \delta}$ are indicative of the activated-type small polaron hopping conductivity below 366 and 392 K respectively. The anisotropic charge transport is influenced only in a limited way by the mixed-valency of Mn prevailing in the manganite spinel blocks. Highly nonlinear current–voltage (I–V) curves with nonlinearity coefficient, $\alpha$, up to 64 was achieved at the turn-on field strength $E_t \sim 110–160 V/mm$. Magnetic properties of $Ca_4Mn_7Zn_3O_{21 -\delta}$ and $Ca_4Mn_7Zn_3O_{19 \pm \delta}$ have been investigated which showed the antiferromagnetic-insulating (AFI) behavior with TN=103 and 80 K and with an AF-ordered effective magnetic moment, $\mu_{eff}=3.54$ and $4.28 \mu _B/Mn$ respectively. The $Ca_4Mn_7Zn_3O_{19 \pm \delta}$ phase showed the ferrimagnetic interaction below $T_N (at \sim 20 K)$

Phase conversions in calcium manganites with changing Ca/Mn ratios and their influence on the electrical transport properties

The phase-interconversions between the spinel-, brownmillerite-, defect rocksalt and perovskite-type structures have been investigated by way of (i) introducing deficiency in A-sites in CaxMn2-xO3 (0.05 <= x <= 1) i.e., by varying Ca/Mn ratio from 0.025 to 1 and (ii) nonstoichiometric CaMnO3-delta (CMO) with 0.02 <= delta <= 1. The temperature dependence of resistivity (rho-T) have been investigated on nonstoichiometric CaMnO3-delta (undoped) as well as the CMO substituted with donor impurities such as La3+, Y3+, Bi3+ or acceptor such as Na1+ ion at the Ca-site. The rho-T characteristics of nonstoichiometric CaMnO3-delta is strongly influenced by oxygen deficiency, which controls the concentration of Mn3+ ions and, in turn, affects the resistivity, rho. The results indicated that the substitution of aliovalent impurities at Ca-site in CaMnO3 has similar effects as of CaMnO3-delta ( undoped) annealed in atmospheres of varying partial pressures whereby electron or hole concentration can be altered, yet the doped samples can be processed in air or atmospheres of higher P-O2. The charge transport mechanisms of nonstoichiometric CaMnO3-delta as against the donor or acceptor doped CaMnO3 (sintered in air, P-O2 similar to 0.2 atm) have been predicted. The rho (T) curves of both donor doped CaMnO3 as well as non-stoichiometric CaMnO3-delta, is predictable by the small polaron hopping (SPH) model, which changes to the variable range hopping (VRH) at low temperatures whereas the acceptor doped CaMnO3 exhibited an activated semiconducting hopping ( ASH) throughout the measured range of temperature (10-500 K)

Effects of Zn substitution on the magnetic and transport properties of La0.6Sr0.4Mn1−yZnyO3−δ(0≤y≤0.3)La_{0.6}Sr_{0.4}Mn_{1-y}Zn_yO_{3-\delta}(0\leq y\leq 0.3)

Phase-singular solid solutions of $La_{0.6}Sr_{0.4}Mn_{1-y}ZnyO_{3-\delta}(0\leq y\leq 0.3)$ [LSMZO] perovskite of rhombohedral symmetry (space group: R3c) with y up to 30 at.% could be synthesized notwithstanding the differences in ionic radii of $Mn_{VI}^{3+}$ (i.r. = 0.645 \AA ) and $Zn^{2+}_{VI}$(i.r. = 0.74 \AA ). The $LSMZO \leq 02$ compositions are ferromagnetic metallic (FMM) at room temperature whereas LSMZO-02–08 are ferromagnetic insulators (FMI) and LSMZO > 08 are paramagnetic insulators (PMI). Total obliteration of the FM transition is unique to Zn-doping at y > 8 at.% leading to PMI even at low temperatures, measured up to 8 K (presently). The FM to PM transition $(T_c)$ and the peak $(T_p)$ in resistivity–temperature curves decreases with the Zn-content. The charge-transport in p-type LSMZO is predictable by variable range hopping (VRH), which changes to nearest-neighbor hopping of small polarons (NNHP) at $T > T_p$. Non-stoichiometry (0.005\leq\delta\leq 0.21) evaluated chemically from redox titrations indicated the prevalence of excess oxygen vacancy $(V_O)$ rather than charge compensatively predictable values which, in turn, indicates the diminishing $Mn^{4+}$ content in LSMZO. The $V_O$’s act as electron donors in p-LSMZO and this increases the resistivity $(\rho RT)$ associated with the shift in $T_c$ to low temperatures. Increased $\rho RT$ on annealing in low $p_{o2}$ is a clear evidence on the role of $V_O$ in LSMZO

Magnetically tuneable nonlinear electronic properties of ZnO/La(Sr)MnO3 ceramic composites

Polycrystalline, multiphase ceramic composites exhibiting voltage-limiting nonlinear current-voltage (I-V) relations with the nonlinearity coefficient ( a) of 220 - 360 have been realized by co-sintering ZnO and La0.6Sr0.4MnO3. The I - V characteristics are symmetrical on voltage reversal to the negative quadrant. By selecting the sintering temperature ( 1573 - 1673 K) and duration ( 1 - 4 h), the interdiffusion of Mn into ZnO and of Zn into La0.6Sr0.4MnO3 could be controlled so that La and Sr segregation leads to the formation of p-type La0.6Sr0.4Mn1-yZnyO3 (LSMZO) permeating along the intergrain regions of n- type ZnO1-gamma : Mn, thereby preserving interior n-p-n heterojunction characteristics at the grain boundaries. Possible mechanisms proposed for large nonlinearity in the I - V curves are (i) avalanche multiplication of minority carrier through impact ionization of majority carriers or (ii) Zener tunnelling of charge carriers across the depleted Schottky potential barriers prevailing at n- ZnO1-gamma : Mn/p-LSMZO ( and p-LSMZO/ n-ZnO1-gamma : Mn) interfaces on the left- and right- hand side of p-LSMZO intergrain phase, wherein the type of conduction mechanism is predominantly dependant on the transport properties and thickness of intergranular LSMZO phase. The I-V characteristics are modified under an applied magnetic field by way of decreasing the turn-on voltage leading to higher currents. Such magnetically tuneable electrical nonlinearity arises from the prevalence of spin-polarized conduction in the ferromagnetic insulating LSMZO which prevails at the intergrain regions of n- ZnO1-gamma : Mn. Magnetization studies of bulk LSMZO show the conversion from ferromagnetic metallic (y > 0.03) to ferromagnetic insulating ( y = 0.03 - 0.08) and paramagnetic insulating ( y > 0.08) phases on increasing the zinc content. However, the n-ZnO1-gamma : Mn grains remain paramagnetic insulator and the magnetically tuneable I - V curves are not dependent on the ferromagnetic ordering therein