User requirement UR1: Robustness of design during normal

(X = Br, Cl)

Por outro lado, foi investigado a dependência das características principais dos modos vibracionais dos compostos multiferróicos isoestruturais, brometo de cobre (CuBr2) e cloreto de cobre (CuCl2) anidros em função da temperatura.

Os espectros Raman em temperatura ambiente conrmam os três modos vibra- cionais previstos pela teroria de grupo, já a análise realizada a cerca da frequência e largura a meia altura dos fônons sob variação de temperatura mostram desvios do comportamento anarmônico previsto por Balkanski, que sugerem uma mudança de fase magnética e são esperados em compostos que apresentam o acoplamento spin-fônon. Uma análise mais aprofundada do desvio dos fônons relacionados com o comportamento magnético foi utilizada. Baseada na composição da susceptibilidade magnética como sendo formada por dois fatores, uma contribuição da susceptibili- dade devido ao ordenamento magnético de longo alcance e outra sendo a contribui- ção devido a interação de baixa dimensão (intra e inter cadeias), com resultados que evidenciam boa concordância com os modelos propostos, mas não em toda faixa de temperatura onde o ordenamento antiferromagnético existe. Essa abordagem é in- teressante e útil quando a magnetização da amostra não é determinada apenas pelo ordenamento de longo alcance, mas também por sistemas de baixa dimensionalidade (intra e inter cadeias).

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ÍNDICE REMISSIVO

A

acoplamento spin-fônon, 4 Air Products and Chemicals, 15 aproximação de campo médio, 9 B

Bruker AXS, 16 Bruker Optics, 15 C

ciência dos materiais, 1 coeciente magnetoelétrico, 3 curvas lorentzianas, 26 E Edwards, 16 espectroscopia Raman, 11 F

física do estado sólido, 1 ferro/antiferromagnetismo, 1 ferroelasticidade, 1

ferroeletricidade, 1

função escalar de correlação de spin, 5

H

Heisenberg, 5

Horiba Jobin Yvon, 14 Horiba Jobin-Yvon, 15 I

integral de troca, 4 L

Linkan Scientic instruments, 15 LynxEye, 16 M magnetoeletricidade, 2 materiais multiferróicos, 1 materiais multifuncionais, 1 modelo de Balkanski, 4 multiferróico magnetoelétrico, 2 N Netzsch, 15 Nikon, 15 O Olympus, 15 46

ÍNDICE REMISSIVO 47 T

tensor de acoplamento spin-fônon, 7 tensor de ligação iônica, 7

tensor potêncial elástico da rede, 7