Tricritical behavior and Griffith phase in La_1-xCa_xMnO₃ under high applied fields

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Studying the magnetic property of La<SUB>0.7</SUB>Ca<SUB>0.3</SUB>MnO<SUB>3</SUB> (LCMO) bulks, it has been found that they exhibit a first-order phase transition (FOPT) around the ferromagnetic-paramagnetic (FM-PM) transition. However, most previous studies just concerned on their magnetic property for applied fields below 60kOe. To learn more about this material system, we have considered the influence of high applied fields up to 140kOe on the magnetic property of a polycrystalline LCMO bulk sample. The detailed analyses based on the Banerjee criterion, Arrott and Kouvel-Fisher methods, and scaling hypothesis prove LCMO exhibiting the first-order phase transition at low applied fields (<I>H</I>) and the tricritical behavior at high applied fields <I>H</I> >65kOe with critical exponents <I>β</I> ≈0.25 and <I>γ</I> ≈1 close to those expected for the tricritical mean-field theory. We have also found a strong dependence of the FM-PM transition temperature (<I>T</I> <SUB>C</SUB>) on <I>H</I> varying as a power function <I>T</I> <SUB>C</SUB>(<I>H</I>)∝ <I>H<SUP>n</SUP> </I> (with <I>n</I> =0.64 and <I>H</I> >3.5kOe), and an existence of the Griffiths phase that is completely suppressed as <I>H</I> ≥35kOe.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High applied fields influence the magnetic properties of La<SUB>0.7</SUB>Ca<SUB>0.3</SUB>MnO<SUB>3</SUB>. </LI> <LI> Transformation from the first order to the crossover of first- and second-order transitions. </LI> <LI> The suppression of Griffiths phase. </LI> </UL> </P>